Abstract
Eight plants of Lamiaceae under subfamily Nepetoideae found in Manipur, India were selected for estimation of their polyphenolic compounds and free radical scavenging activity which is expressed on dry weight basis. In this present study, the total phenol and flavonoid contents as well as the free radical scavenging activity were studied using spectrophotometric method. The total phenol content was determined based on Folin-Ciocalteau reagent, flavonoid was determined by aluminium chloride spectrophotometric method and tannin by Folin Dennis Method. The free radical scavenging activity was determined by using DPPH radical which is expressed as IC50 (μg/ml). The total phenolic content varied from 21.39±0.927 to 46.28±0.543 mg/g, flavonoids content in the selected samples varied from 13.30±0.684 to 26.03±0.217 mg/g and tannin content varied from 8.72±0.160 to 17.04±0.206 mg/g. The free radical scavenging activity among the selected samples varied from 11.67±0.221 to 38.29±0.532 μg/ml. The correlation between the free radical scavenging activity with total phenol content (R2=0.511), with flavonoids (R2=0.241) and with tannin (R2=0.690) was calculated and maximum correlation value was found between tannin content and the free radical scavenging activity of the plant samples. The result supports that tannins were more responsible for free radical scavenging activity in the presently selected plants.
Highlights
Polyphenols are a group of secondary metabolites involved in the H2O2 scavenging in plant cells
Interest in plant materials rich in polyphenolic compounds are on the increase due to their high antioxidant potency, which may offer protection against cancer, through the inhibition of oxidative damage, known to be a potential cause of mutation
Due to large generation of reactive oxygen species such as superoxide radical, hydrogen peroxide, and hydroxyl radical leads to severe effects on the cardiovascular system either through lipid peroxidation or vasoconstriction and other ailments such as inflammation, cancer, diabetes mellitus etc (Lachance et al, 2001; Nickavar et al, 2007)
Summary
Polyphenols are a group of secondary metabolites involved in the H2O2 scavenging in plant cells. Flavonoids and tannins are the most commonly found polyphenolic compounds in plant extracts (Wolfe et al, 2003; Naik et al, 2006). Flavonoids and many other phenolic compounds of plant origin have been reported as scavengers of reactive oxygen species (ROS), and are viewed as promising therapeutic drugs for free radical pathologies (Parshad et al, 1998; Chang et al, 2007).
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