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Enzymes are biologically active complex protein molecules that catalyze most chemical reactions in living organisms, and their inhibitors accelerate biological processes. This review emphasizes medicinal food plants and their isolated chemicals inhibiting clinically important enzymes in common diseases. A mechanistic overview was investigated to explain the mechanism of these food bases enzyme inhibitors. The enzyme inhibition potential of medicinal food plants and their isolated substances was searched in Ovid, PubMed, Science Direct, Scopus, and Google Scholar. Cholinesterase, amylase, glucosidase, xanthine oxidase, tyrosinase, urease, lipoxygenase, and others were inhibited by crude extracts, solvent fractions, or isolated pure chemicals from medicinal food plants. Several natural compounds have shown tyrosinase inhibition potential, including quercetin, glabridin, phloretin-4-O-β-D-glucopyranoside, lupinalbin, and others. Some of these compounds' inhibitory kinetics and molecular mechanisms are also discussed. Phenolics and flavonoids inhibit enzyme activity best among the secondary metabolites investigated. Several studies showed flavonoids' significant antioxidant and anti-inflammatory activities, highlighting their medicinal potential. Overall, many medicinal food plants, their crude extracts/fractions, and isolated compounds have been studied, and some promising compounds depending on the enzyme have been found. Still, more studies are recommended to derive potential pharmacologically active functional foods.

In the present study, two medicinal plants from Africa, namely Bersama abyssinica Fresen. and Scoparia dulcis L., were extracted using ethyl acetate, methanol, and water. The antioxidant, enzyme (α-amylase, α-glucosidase, acetyl- and butyrylcholinesterase, lipase, and tyrosinase) inhibitory action, and phytochemical profiles of extracts of Bersama abyssinica and Scoparia dulcis were determined. The aqueous (180.62 and 61.81 mg gallic acid equivalent/g extract, for B. abyssinica and S. dulcis respectively) and methanol (75.21 and 57.81 mg rutin equivalent/g extract, for B. abyssinica and S. dulcis , respectively) extracts contained high concentrations of phenolic and flavonoids, respectively. The ethyl acetate extracts of both plants were potent inhibitors of α-glucosidase and tyrosinase. Several phytochemical groups were determined by HPLC-MS/MS. The study tend to suggest that B. abyssinica and S. dulcis are potential candidates for the development of novel therapeutical agents.

Ethnobotanical evidences report the use of Rhododendron luteum Sweet (Ericaceae) in traditional medicinal systems. However, R. luteum has been associated to the occurrence of 'mad honey' poisoning. In the present study, the ethyl acetate, methanol, and water extracts of R. luteum were investigated for their in vitro antioxidant, enzyme inhibition, and cytotoxic properties. The cytotoxicity of R. luteum extracts on A549 lung cancer cell line was evaluated using MTT cell viability assay. Besides, HPLC-ESI-MS n approach was employed to elucidate the secondary metabolite profiles of R. luteum in order to establish any structure-activity relationship. Methanol and water extracts of R. luteum possessed highest radical scavenging and reducing properties while the ethyl acetate extract showed highest metal chelating properties. In terms of enzyme inhibition, the methanol and ethyl acetate extracts of R. luteum, possessing epigallocatechin, were active inhibitors of cholinesterase enzymes, α-glucosidase, and tyrosinase. Water extract caused growth inhibition of A549 cells with 207.2 μg/ml IC 50 value. Though R. luteum has received little scientific attention due to the occurrence of grayanotoxins in the plant, however, data presented in this work shows promising biological activity of R. luteum and highlighted its role as a potential source of antioxidant and key enzyme inhibitors., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Although foliar application of seaweed extracts on plant growth and development has and is extensively studied, reliable knowledge and understanding of the mode of action of particular compound(s) responsible for enhancing plant growth is lacking. A brown seaweed Ecklonia maxima is widely used commercially as a biostimulant to improve plant growth and crop protection. Eckol, a phenolic compound isolated from E. maxima has recently shown stimulatory effects in maize, indicating its potential use as a plant biostimulant. Cabbage is a widely cultivated vegetable crop throughout the world, which requires high input of fertilizers and is susceptible to several aphid borne diseases. This study was conducted to evaluate the effect of foliar application of eckol on the growth, phytochemical constituents and myrosinase activity (aphid resistance capacity) of commercially cultivated cabbage. Foliar application of eckol (10(-6) M) significantly enhanced shoot and root length, shoot and root fresh and dry weight, leaf area and leaf number. This treatment also showed a significant increase in photosynthetic pigments (chlorophyll 'a', chlorophyll 'b', total chlorophyll and carotenoid) compared to the untreated plants. The levels of protein, proline and iridoid glycosides were significantly higher in cabbage leaves with eckol treatment. All the control plants were severely infested with cabbage aphid (Brevicoryne brassicae) but no infestation was observed on the eckol-sprayed plants, which can be attributed to an increase in myrosinase activity. This study reveals dual effects (plant growth promoting and insect repelling) of eckol on cabbage plants that need further investigations both under field conditions and in other brassicaceous species., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Enzyme inhibitors are now included in all kinds of drugs essential to treat most of the human diseases including communicable, metabolic, cardiovascular, neurological diseases and cancer. Numerous marine algae have been reported to be a potential source of novel enzyme inhibitors with various pharmaceutical values. Thus, the purpose of this review is to brief the enzyme inhibitors from marine algae of therapeutic potential to treat common diseases. As per our knowledge this is the first review for the potential enzyme inhibitors from marine origin. This review contains 86 algal enzyme inhibitors reported during 1989-2013 and commercial enzyme inhibitors available in the market. Compounds in the review are grouped according to the disease conditions in which they are involved; diabetes, obesity, dementia, inflammation, melanogenesis, AIDS, hypertension and other viral diseases. The structure-activity relationship of most of the compounds are also discussed. In addition, the drug likeness properties of algal inhibitors were evaluated using Lipinski's 'Rule of Five'., (Copyright © 2014 Elsevier Inc. All rights reserved.)