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Seven new oleanane-type triterpenoids (1–7), named fatsicarpains A–G, and the known compounds 3α-hydroxyolean-11,13(18)-dien-28-oic acid (8) and 3α-hydroxyolean-11-en-28,13β-olide (9) were isolated from the leaves and twigs of Fatsia polycarpaon the basis of bioassay-guided fractionation. The structures of compounds 1–7were elucidated through spectroscopic analyses and single-crystal X-ray crystallography of 1, 8, and 9. Cytotoxicity against HepG2 2.2.15 and AGS cells and antihepatitis B virus (HBV) and antibacterial activities of 1–9were also evaluated in vitro.

Few studies have investigated the viral isolation characteristics for severe complicated enterovirus infection (SCEI). This study evaluated the seasonality and contribution of circulated viruses to the chronologic trend and weekly reported SCEI epidemic.

Four new cucurbitane-type triterpenes, cucurbita-5,23( E)-diene-3β,7β,25-triol ( 1), 3β-acetoxy-7β-methoxycucurbita-5,23( E)-dien-25-ol ( 2), cucurbita-5(10),6,23( E)-triene-3β,25-diol ( 5), and cucurbita-5,24-diene-3,7,23-trione ( 6), together with four known triterpenes, 3β,25-dihydroxy-7β-methoxycucurbita-5,23( E)-diene ( 3), 3β-hydroxy-7β,25-dimethoxycucurbita-5,23( E)-diene ( 4), 3β,7β,25-trihydroxycucurbita-5,23( E)-dien-19-al ( 7), and 25-methoxy-3β,7β-dihydroxycucurbita-5,23( E)-dien-19-al ( 8), were isolated from the methyl alcohol extract of the stems of Momordica charantia. The structures of the new compounds were elucidated by spectroscopic methods.

Five new cucurbitane-type triterpenes, (23E)-25-methoxycucurbit-23-ene-3,7-diol (1), (23E)-cucurbita-5,23,25-triene-3,7-diol (2), (23E)-25-hydroxycucurbita-5,23-diene-3,7-dione (3), (23E)-cucurbita-5,23,25-triene-3,7-dione (4), and (23E)-5,19-epoxycucurbita-6,23-diene-3,25-diol (5), together with one known triterpene, (23E)-5,19-epoxy-25-methoxycucurbita-6,23-dien-3-ol (6), have been isolated from the methanol extract of the stems of Momordica charantia. The structures of the new compounds were elucidated by spectroscopic methods.

Three humic substances—humic acid, fulvic acid, and humin—were isolated from soils located in the northern and southern forests of the Yuanyang Lake Nature Preserve in northern Taiwan's Ilan County. Aqueous extracts of fresh wet soil and of three humic substances, at concentrations of 0.125, 0.25, and 0.5 mg/ml, were investigated for their effects on the activities of chlorophyllase a and b. Aqueous extracts of forest soils at the northern and southern bank, dominated by the pure vegetation of Formosan False cypress (Chamaecyparis formosensisMatsum), stimulate both chlorophyllase a and b activities, while those of the southern bank, dominated by a Taiwanese Miscanthus (Miscanthus transmorrisonensisHayata), inhibits such activities. All three humic substances, despite their soil sources, stimulate the activities of both chlorophyllase a and b. Fulvic acid stimulates more chlorophyllase a activity than either humic acid or humin. Humic acid stimulates more activity of chlorophyllase b than either fulvic acid or humin. Humin exhibited the least effect on chlorophyllase a and b. It is suggested that humic substances in the soil may accelerate the chlorophyll degradation of litter in the ecosystem and that chlorophyllase a and b may be different enzymes.

Macaranga tanariusis widely distributed in the abandoned lowlands of Taiwan where substantial amounts of leaves accumulate on the ground. A unique pattern of weed exclusion underneath trees is often found and thought to result from allelopathic interactions. Density-dependent phytotoxicity analysis of Lactuca sativaL. (lettuce) growing in soil mixed with the powder of M. tanariusleaves showed a significant deviation from the expected yield–density relationship. Lettuce growth was most suppressed in the low seed density experiment suggesting that the phytotoxins produced during leaf decomposition inhibit the growth of lettuce seedlings. Bidens pilosaand Leucaena leucocephala, growing in soil mixed with the leaf powder of M. tanariuswere also suppressed. Aqueous leaf extracts were bioassayed against lettuce and B. pilosa, and exhibited a significant suppression in radicle growth. Compounds identified from leaves included nymphaeol-A (1), nymphaeol-B (2), nymphaeol-C (3), quercetin (4), abscisic acid (ABA) (5), blumenol A (6), blumenol B (7), roseoside II (8), tanariflavanone A (9), and tanariflavanone B (10). ABA was the major growth inhibitor. At concentrations of 20 ppm, ABA suppressed lettuce germination, while at 120 ppm it inhibited the growth of Miscanthusfloridulus, Chloris barbata, and Bidens pilosa. At 600 ppm, quercetin, blumenol A, and blumenol B, caused 20–25% inhibition of radicle and shoot growth of M. floridulus. The amount of ABA in M. tanariusleaves was approximately 3–5 μg g−1dry weight, significantly higher than previously reported. We conclude that the pattern of weed exclusion underneath stands of M. tanariusand its invasion into its adjacent grassland vegetation results from allelopathic interactions.

Glycine: was reconstructed based on nucleotide sequences of the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA to examine the systematic status of the G. tomentella and G. tabacina species complexes. Rooted at the subgenus Soja (2 species, 7 accessions), parsimony analysis was conducted for 17 species (31 accessions) of the subgenus Glycine, including 9 and 6 populations of G. tomentella s.l. and G. tabacina s.l., respectively. The nrlTS phytogeny indicated polyphyly of G. tomentella s.l. as well as G. tabacina s.l. In the G. tomentella species complex, larger legumes, narrower leaflets, and deflexed indumentum hairs differentiated G. dolichocarpa from G. tomentella s.s. The tetraploid G. dolichocarpa (2n=80) and aneuploid G. tomentella (2n= 38) represented independent lineages from another clade of the remaining diploid (2n=40) and tetraploid species with a DD genome type. Tetraploid G. tabacina (2n=80) was closely related to G. dolichocarpa instead of the diploid G. tabacina (2n=40) with a BB genome type. The nrlTS phytogeny suggested allopolyploidy of G. dolichocarpa and of the tetraploid G. tabacina, both of which possibly share a common parental species with an AA genome type. Their phylogenetic affinity also indicated biased inheritance of the nrDNA ITS and a possible dominant role of the AA genome. Phylogenetically, G. dolichocarpa and allotetraploid G. tabacina should be recognized as distinct species.

A program of research named Towards an Integrative Biology (TAIB) has recently been promoted by the International Union of Biological Sciences, involving multidisciplinary and interdisciplinary research. Studies of Miscanthusplants which emphasized the TAIB theme were undertaken. Miscanthusspecies are the most widely distributed and dominant species in Taiwan, growing everywhere from the coastal to mountainous areas, and from agricultural to polluted land. Particularly, the grasses grow well in habitats under environmental stresses. Physiological and genetic adaptations are fundamental mechanisms for these grasses' survival in stressful environments. Findings based on field measurements and laboratory analyses were able to elucidate some of the mechanisms of grasses adapted to stressful environments. Adaptive radiation occurred when most niches were open during the postglacial periods. Particularly, population discontinuity of the grasses was found on the Orchid and Green islets of Taiwan. Likewise, Miscanthus sinensisvar. glaberand var. formosanusoccupied lands from low to middle elevations of Taiwan, while Miscanthus transmorrisonensisappeared in the highlands above 2400 m. Phylogenetically, Miscanthushas evolved into various ecotypes, varieties and species in Taiwan as well as in other parts of Asia. The grass then evolved into Miscanthus floridulus, M. sinensisvar. formosanus, Miscanthus flavidus, then to M. transmorrisonensis. Furthermore, the phylogeny of the Miscanthus sinensiscomplex of Taiwan was reconstructed by cladistic analysis on nucleotide sequences of nuclear ribosomal DNA internal transcribed spacers (nrDNA ITS) region and atpB‐rbcL non‐coding spacer of the chloroplast DNA. Rooted at M. floridulusthe monophyly of M. sineneiswas significantly supported by molecular evidence. The origin of this complex could be dated to the last glacial withdrawal about 20 000 years ago.

Acacia confusa(an endemic species) and other introduced species, namely A. aulacocarpa, A. auricumiformis, A. cincinnata, A. crassicarpa, A. leptocarpa, A. margium, A. polystachya, and A. torfiliswere evaluated for allelopathic potential. Among these, A. confusais widely distributed on the hills and lowlands of Taiwn and often exhibits a unique pattern of weed exclusion under stands. Four study sites were selected. Field observations and measurements were carried out at sites that exhibited relatively pure stands of A. confusa. Although the diversity of understory species was comparatively higher in Acaciastands than in adjacent weedy sites, the total coverage and biomass of understory plants was significantly lower than in control sites. Aqueous extracts (0.5%, 1%, 2%, 3%, 4%, and 5%) of dry leaves and litter of Acacia confusaand other species collected from various sites and dates were bioassayed using lettuce, alfalfa, and Chinese cabbage to examine their phytotoxicity. Most extracts exhibited phytotoxicity even at a concentration as low as 0.5%. Inhibition of radicle growth of test plants varied with sampling sites and dates. Bioassay with 5% extracts or above produced more than 85% inhibition of test plants regardless of habitat. In addition, surface soils collected from the upper 20 cm layer of Acaciastands revealed significant inhibition as compared with adjacent grassland control soils. The most inhibitory compounds isolated from the ether fraction of aqueous extracts were identified as: ferulic, vanillic, caffeic, gallic, m-hydroxybenzoic, and m-hydroxyphenylacetic acids. Unidentified flavonoids were also found. Chromatographic bioassays of compounds isolated from both ethyl acetate and water fractions of methanolic extracts of Acacialeaves also showed significant phytotoxicity but none was found in the fractions of chloroform and hexane, suggesting the phytotoxic compounds present in Acaciaplants are water soluble.

A study site located at 2600 m elevation in Tartarchia Anpu, Nantou county, Taiwan, exhibits a unique grassland community composed of two principal species,Miscanthus transmorrisonensis andYushinia niitakayamensis, and 35 other species. The relative frequencies of the two species are 12% and 11%, while their relative coverages are 25% and 19.5%, respectively. The values for the remaining 35 species are lower than4% each, while species diversity of the community is -3.04839, indicating great diversity. To elucidate the mechanism of dominance ofM. transmorrisonensis, allelopathic evaluation of the plant was conducted. Aqueous extracts of M.Transmorrisonensis plant parts with two ecotypes were bioassayed. The extracts showed significant phytotoxic effects on seed germination and radicle growth of four tested plants: rye grass, lettuce, and two varieties of Chinese cabbage. In addition, rhizosphere soils underMiscanthus also exhibited significant phytotoxicity, indicating that allelopathic interaction was involved. Some responsible phytotoxic phenolics, namely, p-coumaric, ferulic, vanillic, protocatechuic, o-hydroxyphenylacetic, andm-hydroxyphenylacetic acids, and 4-hydroxycoumarin and phloridzin were identified. Allelopathy thus can play an important role in regulating plant diversity in the field.

The aqueous extracts of decomposing rice residues in soil exhibited inhibition on the radicle growth of lettuce and rice seeds and the growth of rice seedlings. The phytotoxicity was found in extracts obtained from the early stage of decomposition (first month), and gradually declined thereafter. The inhibition was also found in extracts obtained from rice fields, and was persistent for 4 months. The root initiation of hypocotyl cuttings of mungbeans was suppressed by extracts of decaying rice residues and extracts obtained from paddy soil. Five phytotoxins,p-hydroxybenzoic,p-coumaric, vanillic, ferulic, ando-hydroxyphenylacetic acids, and several unknowns were found in the decomposing rice residues under waterlogged conditions. At 25 ppm,o-hydroxyphenylacetic acid revealed significant inhibition on the radicle growth of rice and lettuce seeds and suppressed root initiation of mungbean seedlings. It was concluded that the growth of rice seedlings was retarded by decaying rice residues in soil; thus, this appeared to be an autointoxication phenomenon.

Residues from corn and rye plants were allowed to decompose in soil for periods up to 30 days at 22–23 °C, and the identity of some of the compounds produced as well as their relative phytotoxicity to lettuce seed and seedlings were determined. Paper, thin-layer, and gas chromatography were the principal methods used to identify the various compounds formed. The identities were confirmed by comparison with known synthetic compounds. Eighteen compounds were identified in the decomposing corn residues. Of these, salicylaldehyde, and butyric, phenylacetic, and 4-phenylbutyric acids were “volatile”, and benzoic,p-hydroxybenzoic, vanillic, ferulic,o-coumaric,o-hydroxyphenylacetic, salicylic, syringic,p-coumaric,trans-cinnamic, and caffeic acids were “not volatile”. Resorcinol,p-hydroxybenzaldehyde, and phloroglucinol were also found. In the decomposing rye residues, nine compounds were identified, including vanillic, ferulic, phenylacetic, 4-phenylbutyric,p-coumaric,p-hydroxybenzoic, salicylic, ando-coumaric acids, and salicylaldehyde. In the lettuce seed bioassay, most of the above compounds from corn and rye decomposition products exhibited some phytotoxicity. Phenylacetic, 4-phenylbutyric, salicylic, benzoic, ando-hydroxyphenylacetic acids were highly inhibitory to the growth of lettuce at concentrations between 25 and 50 ppm. The others reduced growth significantly at 100 ppm. Most of the phototoxic spots were located in theRf0.37–0.97 zone when developed in 2% acetic acid solvent.

A unique pattern of weed exclusion was found under the canopy ofDelonix regia, which was planted in many places as an ornamental tree in the south of Taiwan. A quadrat method was employed to examine the botanical composition between the area underneathD. regia and its adjacent control grassland. The number of species and coverage of understory species were significantly lower in the area of theD. regia than that of the grassland, indicating the growth of understory species was suppressed byD. regia. A series of aqueous extracts of leaves, flowers, and twigs ofD. regia were bioassayed against three species to determine their phytotoxicity, and the results showed highest inhibition in the flowers. A water-culture experiment indicated the aqueous extract of flowers ofD. regia on two local understory species (Isachne nipponensis andCentella asiatica) inhibited growth of both species by more than 70%. The phytotoxicities of fallen leaves and flowers ofD. regia were not significantly affected by temperature. When the plant material was subjected to temperatures above 70°C, however, phytotoxicity was decreased, indicating that the allelopathic nature ofD. regia could easily be decomposed by fire. By means of paper, thin-layer, and high-performance liquid chromatography, and UV-visible spectrophotometry, responsible phytotoxins present in leaves, flowers, and twigs ofD. regia were identified as 4-hydroxybenzoic, chlorogenic, 3,4-dihydroxybenzoic, gallic, 3,4-dihydroxycinnamic, 3,5-dinitrobenzoic, and L-azetidine-2-carboxylic acids, and 3,4-dihydroxybenzaldehyde. The findings of bioassays and the number and amount of responsible allelopathic compounds found inD. regia are well correlated, thus permitting the conclusion that the exclusion of understory plants under the canopy ofD. regia trees was due primarily to the allelopathic effect of the fallen flower, leaves, and twigs of theD. regia. A possible mechanism of action is discussed.

The phytotoxicity of plant leachates was evaluated from four subtropical grasses:Brachiaria mutica, Digitaria decumbens, Imperata cylindrica var. Major, andPanicum repens. The aqueous leachate of each grass was used to water the growth of the four grasses in pots. The leachates exhibited variable inhibition of grass growth as compared to the tap water control. By the 41st day after treatment, the leachate ofD. decumbens significantly suppressed the growth of itself and retarded that ofB. mutica andP. repens. The growth ofB. mutica was inhibited by its own leachate, but that ofI. cylindrica was not affected by any of the grass leachates. In crop growth rate (CGR) analysis, the four grass leachates exhibited a similar inhibition pattern. In laboratory bioassays, the leachates showed a significant phytotoxic effect on the radicle growth of ryegrass and lettuce. Six phytotoxic phenolics were quantitatively compared by high-performance liquid chromatography, and the amount of compounds varied with species. The highest total amount of phytotoxic phenolics occurred inD. decumbens, followed, in decreasing order, byP. repens, B. mutica, andI. cylindrica. These findings show that the leachates of four grasses possess phytotoxic compounds that may play a significant role in grass dominance in the field.

Leucaena leucocephala plantations in Kaoshu, southern Taiwan, exhibit, after several years of growth, a unique pattern of weed exclusion beneathLeucaena canopy. The pattern has been observed in manyLeucaena plantations in Taiwan and is particularly pronounced in the area where a substantial amount ofLeucaena litter has accumulated on the ground. Field data showed that the phenomenon was primarily not due to physical competition involving light, soil moisture, pH, and nutrients. Instead, aqueous extracts ofLeucaena fresh leaves, litter, soil, and seed exudate showed significantly phytotoxic effects on many test species, including rice, lettuce,Acacia confusa, Alnus formosana, Casuarina glauca, Liquidambar formosana, andMimosa pudica. However, the extracts were not toxic to the growth ofLeucaena seedlings. The decomposing leaves ofLeucaena also suppressed the growth of the aforementioned plants grown in pots but did not inhibit that ofLeucaena plants. By means of paper and thin-layer chromatography, UV-visible spectrophotometry, and high-performance liquid chromatography, 10 phytotoxins were identified. They included mimosine, quercetin, and gallic, protocatechuic,p-hydroxybenzoic,p-hydroxyphenylacetic, vanillic, ferulic, caffeic, andp-coumaric acids. The mature leaves ofLeucaena possess about 5% dry weight of mimosine, the amount varying with varieties. The seed germination and radicle growth of lettuce, rice, and rye grass were significantly inhibited by aqueous mimosine solution at a concentration of 20 ppm, while that of the forest species mentioned was suppressed by the mimosine solution at 50 ppm or above. However, the growth ofMiscanthus floridulus andPinus taiwanensis was not suppressed by the mimosine solution at 200 ppm. The seedlings ofAgeratum conzoides died in mimosine solution at 50 ppm within seven days and wilted at 300 ppm within three days. It was concluded that the exclusion of understory plants was evidently due to the allelopathic effect of compounds produced byLeucaena. The allelopathic pattern was clearly shown in the area with a heavy accumulation ofLeucaena leaf litter, which was a result of drought and heavy wind influence.

The phytotoxicity produced during decomposition of rice straw in soil was evaluated under both constant and changing temperature conditions. Bioassay tests showed that the aqueous extract from a soilstraw mixture after incubation at constant temperature was more than twice as phytotoxic as the extract from soil incubated alone. The phytotoxicity was highest at 20–25 ° C. Temperatures above 25 ° C enhanced rice straw decomposition and also degraded the phytotoxic substances more rapidly. After incubation of soil mixtures under changing temperature regimes in a phytotron, the phytotoxicy of the soil aqueous extracts increased in the following order: soil alone < soil + fertilizer < soil + straw < soil + straw + fertilizer. Growth inhibition of lettuce or rice seedlings was also at the highest at the temperature range of 25–30 ° C irrespective of the direction of temperature changes from either low to high or vice versa. Five phytotoxic phenolics,p-hydroxybenzoic, vanillic,p-coumaric, syringic, and ferulic acids, were obtained from both the aqueous extract and residue of the incubated soil samples and were quantitatively estimated by chromatography. The amount of phytotoxins found in various soil mixtures followed the same increasing order as that found by the seed bioassay test. Although no definite distribution pattern of the phenolics in the incubated soil samples can be attributed to temperature variations, the amount of the phenolics was likely higher in the samples incubated at 25 ° C than at either 15 ° C or 35 ° C. The quantity of toxins released during decomposition of rice straw in soil reached highest levels six weeks after incubation and gradually disappeared after twelve weeks.

Allelopathic compounds, including fatty acids, phenolics, flavonoids, terpenoids, and alkaloids, have been found in various plants and soils of different habitats in Taiwan since 1972. For example, in a monoculture of rice plants, phytotoxins were produced during the decomposition of rice residues in soil, suppressed the growth of rice seedlings, and reduced the numbers of tillers and panicles, leading to yield reduction. The allelopathic metabolites are also affected by environmental factors, such as oxygen, temperature, soil moisture, microbial activity, and levels of fertilizers in soil, and allelopathy was pronounced in areas where environmental stresses were severe. Substantial amounts of phytotoxic mimosine and phenolics were released into soil by plant parts of Leucaenaleucocephala, and these suppressed the growth of many understory species except that of L.leucocephala itself. A unique pattern of absence of understory plants was ubiquitous beneathPhyllostachys edulis, due primarily to an allelopathic effect. In a forest pasture intercropping, an aggressive kikuyu grass was planted in a deforested land where Chinese fir grew previously, to help in understanding the mechanism of biological interactions between plants. Aqueous soil leachate and extracts of the grass significantly, retarded the growth of local weeds but not that of the Chinese fir. Allelopathy thus plays an appreciable role in natural vegetation and plantations in Taiwan.

The aqueous extracts of leaves, stems, and roots ofCoffea arabica significantly inhibited the seed germination and radicle growth of rye grass, lettuce, and fescue. When the extracts were diluted to 1% solution, significant suppression of lettuce growth was still found and was particularly pronounced in the extract of young seedlings. The paper chromato-gram of the ether fraction of an aqueous extract of coffee leaves was bioassayed with lettuce seeds and revealed a remarkable inhibition throughout the chromatogram except for the segment ofRf 0.00–0.12. Paper without spotting extract was used as a standard. The phytotoxins present in coffee tissue were identified by paper and thin-layer chro-matography and mass spectrometry. The compounds include caffeine, theobromine, theophylline, paraxanthine, scopoletin, and chlorogenic, ferulic,p-coumaric,p-hydroxybenzoic, caffeic, and vanillic acids. All compounds except caffeic acid exhibited significant phytotoxicity to lettuce growth at a concentration of 100 ppm.

Ammonium sulfate and potassium nitrate added as a top dressing and rice straw were incorporated into soil to understand their effect on the chemical nature of the paddy soil and on the growth and yield of rice plants during two successive crop seasons. Redox potential (Eh) determination indicated that the paddy soil appeared to be the reduced form in mixture with rice residues. The amounts of ammonium nitrogen (NH4+—N) and nitrate nitrogen (NO3-—N) were significantly higher in the second crop than in the first crop, and the quantity of NH4+—N was about 10 times greater than that of NO3-—N. The incorporation of rice straw decreased both the available nitrogen and the soil cations, Zn2+, Cu2+, Ca2+, Mn2+, and Na+. The quantity of Zn2+, Cu2+, Mg2+, and Na+ was significantly lower in the second crop that that in the first. The growth and yield of rice plants were significantly affected by cultural treatment; thus the ammonium sulfate dressing treatment resulted in higher yields than the potassium nitrate treatment. The NH4+—N treatment had an antagonistic effect on the phytotoxic nature of rice straw decomposed in soil. The phytotoxicity (primarily phenolic type compounds) of aqueous extracts of soil varied between treatments and was significantly higher in the soil which had been mixed with rice straw. This finding correlated well with the higher amounts of phytotoxic plant phenolics produced by the decomposing rice residues in the soil.

On many hillsides of Taiwan there is a unique pattern of weed exclusion byPhyllostachys edulis (bamboo) andCryptomeria japonica (conifer) in which the density, diversity, and dominance of understory species are very different. Although the physical conditions of light, soil moisture, and soil nutrients strongly favor the growth of understory in a bamboo community, the biomass of its undergrowth is significantly low, indicating that physical competition among the understory species in the bamboo and conifer communities does not cause the observed differences. However, the biochemical inhibition revealed by these two plants appeared to be an important factor. The growth ofPellionia scabra seedlings, transplanted from the study site into greenhouse pots, was evidently suppressed by the aqueous leachate of bamboo leaves but was stimulated by that of conifer leaves. The radicle growth of lettuce, rye grass, and rice plants was also clearly inhibited by the leachate and aqueous extracts of bamboo leaves but not by those of conifer leaves. Six phytotoxins,o-hydroxyphenylacetic,p-hydroxybenzoic,p-coumaric, vanillic, ferulic, and syringic acids were found in the aqueous leachate and extracts of leaves and alcoholic soil extracts ofP. edulis, while the first three compounds were absent in the extracts ofC. japonica. The phytotoxicities of extracts were correlated with the phytotoxins present in both leaves and soils. The understory species might be variously tolerant to the allelopathic compounds produced by the two plants, resulting in a differential selection of species underneath. Therefore, comparative allelopathic effects ofPhyllostachys edulis andCryptomeria japonica may play significant roles in regulating the populations of the understories.

Aqueous extracts of 12 subtropical grasses inhibited seed germination and radicle growth ofLactuca sativa var. Great Lakes at osmotic concentrations as low as 10 milliosmol.Acroceras macrum,Chloris gayana, Digitaria decumbens, andPanicum maximum exhibited the highest inhibition, whileCortaderia selloana revealed the least. Toxic spots were found on chromatograms of the ether fraction of aqueous extracts.Cynodon dactylon, Setaria sphacelata, andTripsacum laxum showed more than six toxic spots, whileAndropogon nodosum,Bracharia mutica, andChloris gayana gave less than three toxic spots. The phytotoxins ferulic, syringic,p-coumaric, vanillic,p-hydroxybenzoic, ando-hydroxyphenylacetic acids were identified. These compounds are differentially distributed in the 12 grasses studied. Additionally, most of these compounds were also found in the associated soils; the control (nonherb-growth) soil provided the toxic compounds in significantly less amount than did the grass soils.

Allelopathic compounds are metabolites released from plants that might be beneficial or detrimental to the growth of receptor plants. These compounds are involved in the environmental complex of managed or natural ecosystems. Allelopathic compounds have been shown to play important roles in the determination of plant diversity, dominance, succession, and climax of natural vegetation and in the plant productivity of agroecosystems. The overuse of synthetic agrochemicals often causes environmental hazards, an imbalance of soil microorganisms, nutrient deficiency, and change of soil physicochemical properties, resulting in a decrease of crop productivity. The incorporation of allelopathic substances into agricultural management may reduce the use of synthetic herbicides, fungicides, and insecticides and lessen environmental deterioration. Scientists in many different habitats around the world have demonstrated the above examples previously. It is known that most volatile compounds, such as terpenoids, are released from plants in drought areas. In contrast, water-borne phytotoxins, such as phenolics, flavonoids, or alkaloids, are released from plants in humid zone areas. Both allelopathy and autointoxication play an important mechanism in regulating plant biodiversity and plant productivity. A unique case study of a pasture-forest intercropping system, which is particularly emphasized here, could be used as a model for forest management. After the deforestation of coniferous or hardwood forests, a pasture grass, kikuyu grass (Pennisetum clandestinum), was transplanted onto the land. The grass was quickly established within 6 months. Significant suppression of weed growth by the kikuyu grass was found; however, the growth of coniferous or hardwood plants was not suppressed but stimulated. This example as well as others described in this text clearly indicate that allelopathy plays a significant role in sustainable agriculture. Nevertheless, room for allelopathic research in the next century is available for biologists, biochemists, biotechnologists, and chemists. Future allelopathic research should focus on the following tasks: (1) a continuous survey of potential allelochemicals from natural vegetation or microorganisms, (2) the establishment of practical ways of using allelochemicals in the field, (3) to understand the mode of action of allelopathic chemicals in receptor organisms, (4) to understand the role of allelopathic chemicals in biodiversity and ecosystem function, (5) to explore advanced biotechnology for allocating allelopathic chemical genes in plants or microorganisms for biological control, and (6) to challenge the natural product chemists to develop a better methodology for isolating allelopathic compounds or their degraded compounds from the environment, particularly the soil environment.

Miscanthus, a genus of the Poaceae, has attracted biologists' attention because of its high biomass and fast growth, traits that make this grass potentially useful as a biofuel. Miscanthus, is morphologically diverse and widespread across various habitats along altitude and latitude, providing a perfect model for investigating adaptation and speciation. Nevertheless, big genome sizes and rampant gene flow cause challenges in the genomic analysis of species swarms of Miscanthus. Here, we illustrate genetic and genomic analyses of divergence and adaptive differentiation among Miscanthusspecies. Outlier and linkage disequilibrium analyses are suggested for the identification of genes under diversifying selection.

Fatsia polycarpaHayata is an evergreen shrub endemic to Taiwan and used locally to treat several inflammatory disorders. The crude extract of F. polycarpahas been proven to exhibit an anti-inflammatory effect in vitroand in vivo; however, which constituents of the extract confer the anti-inflammatory function remains unclear. Fatsicarpain D (Fat D) and fatsicarpain F (Fat F) are oleanane-type triterpenoids and two of the feature constituents of the F polycarpaextract. Ester substitution on C-3 has been proposed to enhance the activities of triterpenoids. Thus, this study compared and characterized the anti-inflammatory activities of Fat D, Fat F, and the C-3-acetylated derivatives thereof. These compounds were toxic to RAW 264.7 cells, but not to FL83B cells. The compounds dose-dependently inhibited tumor necrosis factor-α (TNF-α)-induced expression of inducible nitric oxide synthase in FL83B cells, with the IC50values being Fat D 8.5 μM, acetylated Fat D 10.4 μM, acetylated Fat F 10.7 μM, and Fat F 27.4 μM, respectively. Thus, acetylation of C-3 improved the activity of Fat F. Moreover, the compounds suppressed TNF-α-induced expression of nuclear factor-κB (NF-κB) p65 subunit and protein tyrosine phosphatase-1B. Furthermore, they inhibited TNF-α-mediated activation of the inhibitor kappa B kinase (IKK), and that of the mitogen-activated protein kinases (MAPKs) extracellular-signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK), but promoted the activation of MAPK p38, which was found to be anti-inflammatory in certain cell types. Thus, Fat D and Fat F exhibited obvious anti-inflammatory activities in vitroand inhibited ERK, JNK, and the IKK/NF-κB pathway.

Eleven compounds were isolated from the methanol extract of the leaves of Solanum erianthumD. Don, including five α-linolenic acid analogs, α-linolenic acid (1), 13 S-hydroxy-9(Z),11(E)-octadecadienoic acid (2), 9S-hydroxy-10(E),12(Z), 15(Z)-octadectrienoic acid (3), 9(Z),11(E)-octadecadienoic acid (4), and octadecanoic acid (5); two benzofuran-type lactones, loliolide (6) and dihydroactinidiolide (7); two steroidal alkaloids, solasonine (8) and solamargine (9); a flavonol glycoside, camelliaside C (10); and a flavone, 5-methoxy-(3″,4″-dihydro-3″,4″-diacetoxy)-2″,2″-dimethylpyrano-(7,8:5″,6″)-flavone (11). Among these isolated compounds, 9showed the most potent activity against HBsAg, with an IC50of 1.57 μM, followed by 8(IC50is 5.89 μM). In the testing against HBeAg, 11was the only active compound with an IC50of 36.11 μM. Compound 9also revealed strong inhibition of DNA replication towards HBV and its IC50was 2.17 μM. However, α-linolenic acid (1) showed a prominent selected index (SI), both in anti-HBsAg and inhibition of DNA replication with SI values of 7.75 and 7.18, respectively. This is the first report that unsaturated fatty acid 1, steroidal alkaloid glycoside 9and flavone 11, all showed excellent activity against HBV. These results provide lead candidates in the development of anti-HBV drugs from natural sources.

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Eighteen components were isolated from the methanolic extract of leaves of Rhododendron formosanum Hemsl. (Ericaceae), an endemic species in Taiwan, and evaluated for their allelopathic properties. Of the isolated compounds, 3 β-friedelinol, 5,6β-epoxy-5β-stigmastan-3β-ol, 5,6α-epoxy-5α-stigmastan-3 β-ol, lupeol and ursolic acid revealed inhibitory effects at 10−4M or above, whereas α-tocopherol, friedelin and β-amyrin acetate exhibited stimulatory effects on the radicle growth of the test plants at the same concentration or above. However, squalene and α-amyrin showed either a stimulatory or inhibitory effect. The remaining four components, coumarin, β-sitosterol, adian-5-en-3β-ol and 3β-acetoxyurs-12-en-28-al, were not significantly effective in the present bioassay, but have been reported as allelopathic agents elsewhere.

Nine components were isolated from the methanol extract of the whole herb of Polygonum perfoliatumand evaluated for their antioxidant activity. Among them, α-tocopherol and methyl trans-ferulate showed significant DPPH free radical scavenging effects with EC50values of 11.9 and 7.8 μg/mL, respectively. In addition, five phenolic acids, caffeic acid, p-coumaric acid, p-hydroxybenzoic acid, protocatechuic acid, and vanillic acid were isolated from the aqueous extracts of the plant and identified by means of paper and high performance liquid chromatography. These five compounds were confirmed to be allelopathic substances by bioassay against the radicle growth of lettuce (Lactuca sativa), Chinese cabbage (Brassica oleracea), and radish (Raphanus acanthiformis).

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