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Evaluation of Phenolic Compounds and 时间:2017-05-25 14:47 来源:未知作者:admin 点击: 次 Abstract:The study was designed to evaluate the phenolic, flavonoid contents and antioxidant and antimicrobial activities of onion (Allium cepa), garlic (Allium sativum), mint (Mentha spicata), thyme (Thymus vulgaris), oak (Quercus), aloe vera (Aloe barbadensis Miller), and ginger (Zingiber officinale). All extracts showed a wide range of total phenolic contents, that is, 4.96 to 98.37 mg/100 g gallic acid equivalents, and total flavonoid contents, that is, 0.41 to 17.64 mg/100 g catechin equivalents. Antioxidant activity (AA) was determined by measuring reducing power, inhibition of peroxidation using linoleic acid system, and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) scavenging activity. Different extracts inhibited oxidation of linoleic acid by 16.6–84.2% while DPPH radical scavenging activity (IC50 values) ranged from 17.8% to 79.1 μg/mL. Reducing power at 10 mg/mL extract concentration ranged from 0.11 to 0.84 nm. Furthermore the extracts of these medicinal herbs in 80% methanol, 80% ethanol, 80% acetone, and 100% water were screened for antimicrobial activity by disc diffusion method against selected bacterial strains, Staphylococcus aureus, Escherichia coli, Bacillus subtilis, and Pasteurella multocida, and fungal strains, Aspergillus niger, Aspergillus flavus, Rhizopus solani, and Alternaria alternata. The extracts show better antimicrobial activity against bacterial strains as compared to fungal strains. Results of various assays were analyzed statistically by applying appropriate statistical methods.
1. Introduction
In developing countries, 65%–80% of population depends upon herbal medicines for primary health care [1]. Different categories of bioactive compounds are being isolated and characterized since the middle of 19th century. Most of these compounds are used as raw material for new medicines or as an active ingredient of existing medicines. Herbal medicines provide rich amount of tannins, alkaloids, flavonoids, phenolic compounds, and so forth, so these can be used in the treatment of several degenerative disorders [2, 3].
Antioxidants play a vital role in free radical scavenging and chain breaking of oxidation reactions both in vivo and in vitro. Free radicals possess free unpaired electrons, making them highly unstable and can extract electron from other molecules to attain stability causing them damage. Among the potential uses of antioxidants, some are prevention of diseases related to oxidative stress in humans and also prevention of oxidative reactions in pharmaceuticals, cosmetic products, and food [4].
Utilization of synthetic antioxidants, that is, citric acid, propyl gallate, butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) in foods, leads to many side effects. For instance, these synthetic antioxidants have carcinogenic effect in living systems and many reports indicated that they may enhance microsomal enzyme activity and also enlarge liver size. Consequently, there is an increase interest in finding natural antioxidant agents capable of scavenging free radicals and hindering oxidative rancidity of lipids, in this way, protecting living organisms from diseases and retarding food spoilage [5].
Vegetables, grains, and fruits contain a huge variety of bioactive phytochemicals. The antioxidants which are derived from plants may function as free radicals scavengers, metal ion chelators, and reducing agents. It has been demonstrated that plasma antioxidant activity increases after consuming food high in antioxidants. That is why phytochemicals may fight against oxidative stress by maintaining a balance between antioxidants and oxidants. Many medicinal plants possess antioxidant properties. Antioxidants extracted from plants either in form of raw extracts or as their chemical constituents are very effective to stop the destructive processes caused by oxidative stress [6,7].
Our aim was to evaluate the antioxidant, antibacterial, and antifungal activities, total flavonoid contents, and total phenolic contents of 6 commonly medicinal plants, onion (Allium cepa), garlic (Allium sativum), mint (Mentha spicata), thyme (Thymus vulgaris), oak (Quercus), aloe vera (Aloe barbadensis Miller), and ginger (Zingiber officinale). Antioxidant activity was determined by measuring inhibition of peroxidation using linoleic acid system, measuring reducing power and DPPH scavenging activity. Antimicrobial activity was determined by disc diffusion assay against four selected bacterial strains, Pasteurella multocida, Staphylococcus aureus, Bacillus subtilis, and Escherichia coli, and four fungal strains, Alternaria alternata, Aspergillus niger, Rhizopus solani, and Aspergillus flavus.