Phenolics from Mikania micrantha and Their Antioxidant Activity

Abstract

A phytochemical study on the aerial parts of Mikania micrantha led to the isolation of two new phenolic compounds, benzyl 5-O-β-d-glucopyranosyl-2,5-dihydroxybenzoate (1) and (7S,8R)-threo-dihydroxydehydrodiconiferyl alcohol 9-acetate (2), together with twelve known compounds, benzyl 2-O-β-d-glucopyranosyl-2,6-dihydroxybenzoate (3), 4-allyl-2,6-dimethoxyphenol glucoside (4), (+)-isolariciresinol (5), icariol A2 (6), 9,10-dihydroxythymol (7), 8,9,10-trihydroxythymol (8), caffeic acid (9), p-coumaric acid (10), ethyl protocatechuate (11), procatechuic aldehyde (12), 4-hydroxybenzoic acid (13), and hydroquinone (14). Their structures were elucidated on the basis of extensive spectroscopic analysis. Except 8 and 9, all the other compounds were isolated from this plant species for the first time. The antioxidant activity of those isolated compounds were evaluated using three different assays. Compounds 1, 2, 3, 9, 10, 13, and 14 demonstrated significant 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) free radical cation scavenging activity ranging from SC50 0.31 to 4.86 µM, which were more potent than l-ascorbic acid (SC50 = 10.48 µM). Compounds 5, 9, 11, and 12 exhibited more potent 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (SC50 = 16.24–21.67 µM) than l-ascorbic acid (39.48 µM). Moreover, the ferric reducing antioxidant power (FRAP) of compounds 2, 5, 9, and 11 were discovered to be also comparable to or even more potent than l-ascorbic acid.

Chemical Constituents from Scindapsus officinalis (Roxb.) Schott. and Their Anti–Inflammatory Activities

“…The EtOAc fraction was subjected to diverse column chromatography to furnish seven compounds, including one new monoterpene glycoside ( 1 ), one new phenyl glycoside ( 2 ), one new caffeoyl derivative ( 3 ), and four known compounds ( 4 – 7 ). By comparison with previous NMR data in the literature, the known compounds were identified as caffeic acid ( 4 ) [ 10 ], 2-phenylethyl β - d -Glucopyranoside ( 5 ) [ 11 ], hexyl- O - β - d -Glucopyranoside ( 6 ) [ 12 ], and methyl gallate ( 7 ) [ 13 ], which were isolated from S. officinalis for the first time.…”

2-Phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide Radical (PTIO•) Trapping Activity and Mechanisms of 16 Phenolic Xanthones

“…The reason why the ortho -di-OHs play a critical role in antioxidant xanthones may be the fact that ortho -di-OHs can be oxidized to ortho -benzo quinone by free radicals [ 27 , 28 ]. For example, in the reaction of isojacareubin with PTIO•, 5,6-di-OHs is oxidized to 5,6- ortho -benzoquinone via ET plus H + -transfer mechanisms [ 29 , 30 ] ( Figure 4 ). Similarly, para -di-OHs type could be hypothesized to transform into para -benzoquinone, in accordance with Figure 4 .…”

Missing Data Calculation Using the Antioxidant Activity in Selected Herbs

“…Natural antioxidants can help preventing oxidation and regulate the immune function [7]. Overproduction of free radicals can cause oxidative damage to biomolecules.…”