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The composition of the essential oil from the leaves of Cistus monspeliensis (Cistacea) shows seasonal and diurnal variation. The essential oils were investigated by GC-FID and GC-MS. Labdanes which were identified for the first time in the essential oil of C. monspeliensis, are predominant in autumn and in winter and they were found in great amount with clerodanes in spring. Manoyl oxide, 3β-hydroxy-13-epi-manoyl oxide, 3β-acetoxy-13-epimanoyl oxide and their isomers varied through the day and the year. The results obtained fro GC-MS analysis of the oils were submitted to statistical analysis. © 2002 Elsevier Science Ltd. All rights reserved.

The composition of the essential oils of fifteen populations of Cistus salviifolius L. (Cistaceae) from Crete (Greece) and their interpopulation variability was investigated by GCMS. 167 compounds were identified representing an average of 96-100% of the oil composition. Labdane diterpenes were detected and identified in the essential oils of Cistus salviifolius L., for the first time. The results obtained from GC-MS analysis of the oils were submitted to a Principal Component Analysis (PCA). Three main chemotypes (clusters) were differentiated. All the essential oils were tested for their antimicrobial activity against Gram-positive and Gram-negative bacteria. Only chemotype III having camphor as a major constituent was active against Gram-positive bacteria. Camphor, viridiflorol, longiborneol, phyllocladene, abietatriene and cis-feruginol are the main constituents, while the group of oxygenated sesquiterpenes has the highest percentage composition. © 2002 Elsevier Science Ltd. All rights reserved.

Essential oils and hexane extracts from Cistus monspeliensis L. leaves and fruits were analysed by GC-MS. Manoyl oxide and its isomers, 3β-hydroxy-manoyl oxide, 3β-hydroxy-13-epi-manoyl oxide, as well as 3β-acetoxy-13-epi-manoyl oxide were detected for the first time in C. monspeliensis L. Ent-13-epimanoyl oxide was isolated from the hexane extract of leaves and its structure was determined using spectroscopic methods. In vitro cytotoxic activity of ent-13-epi-manoyl oxide and mixtures of manoyl oxide isomers at 10-4 M concentrations ranged from 11.1 to 32.2% of the activity for a vinblastine control evaluated against nine leukemic cell lines. The results showed that the manoyl oxide isomer mixtures as well as ent-13-epi-manoyl oxide exhibited a slight growth inhibiting activity.

The composition of the essential oils of nine populations of Cistus parviflorus L., from Crete (Greece) and their interpopulation variability, were investigated by GC-MS. 114 compounds were identified representing an average of 85-96% of oil composition. Labdane diterpenes were detected and identified in the essential oils of Cistus parviflorus L. for the first time. The results obtained from GC-MS analysis of the volatile oils were submitted to principal component and chemometric cluster analysis. Two main chemotypes (clusters) were differentiated; the first of West Crete and the second of East Crete. Carvacrol, caryophyllene oxide, α-epi-cadinol, abietatriene, 4-epi-dehydroabietol, dehydro abietol, cis-ferruginol and manoyl oxide mixture of isomers are the main constituents, while oxygenated sesquiterpenes as well as diterpenes have been found in high percentage composition. © 2001 Elsevier Science Ltd.

The membrane perturbing 3, 7, 4′, 5′-tetramethyl ether of myricetin 1 was isolated from Cistus monspeliensis L. Its structure was elucidated and its conformational properties were explored using a combination of 2D NMR spectroscopy and computational chemistry. The obtained results showed that compound 1 adopts four enantiomeric pairs of low energy conformers characterized: (a) by an aromatic ring B twisted through rotation about C2-C1′ bond from the rigid isoflavone ring; (b) a 4′-O-CH3 bond oriented out of the plane with equal probability upwards or downwards the phenyl ring B, while all the other O-CH3 bonds are oriented in the plane of the aryl ring. Two of these enantiomeric pairs are lowest in energy. These possible bioactive conformers are possibly stabilized by van Der Waals interactions. The 3′, 5-diacetyl derivative 2 of compound 1 was synthesized and its structure elucidation was achieved based on the chemical shift assignment of the parent compound 1. The Differential Scanning Calorimetry (DSC) results revealed that the degree of the thermal effects exerted by the flavonoids at dipalmitoylphosphatidyl choline (DPPC) bilayers followed the order 1 > 2 > myricetin. Their antimicrobial activity against Gram positive bacteria followed the same order.

Two labdane type diterpenes, labd-13(E)-ene,-8 alpha ,15-diol (1) and labd-13(E)-ene,-8 alpha ,15-yl acetate (2) were isolated from the hexane extract of Cistus creticus subsp. eriocephalus (Viv.) Greuter & Burdet leaves, while (+)-19-acetoxy-cis-clerodan-3-en-15-oic acid (3) was isolated from the hexane extract of Cistus monspeliensis L. leaves. The compounds were examined for their in vitro cytostatic and cytotoxic activity against nine human leukemic cell lines, three of which exhibited a multidrug resistant phenotype. They were also evaluated for their anti-inflammatory activity in vivo on the back of hairless mice. The cytostatic and cytotoxic activity of the tested diterpenes followed the order 1 >2 >3. Topical application of the diterpenes on barrier disrupted skin did not seem to have a significant contribution to the repair rate of the skin barrier.

Two myricetin derivatives, the 3,7,4',5'-tetramethyl ether of myricetin (1), isolated from the hexane extract of Cistus monspeliensis, and its 3',5-diacetyl derivative (2) which was synthesized, and the parent compound, myricetin (3), were examined for their in vitro cytotoxic activity against nine human leukemic cell lines, two of which were mdr cell lines. Compound 2 exhibited higher cytostatic and cytotoxic activities in comparison to compound 1, while compound 3 was inactive against all tested cell lines. Vinblastine was used as a control. (C) 2000 Academic Press.