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Indoline Amide Glucosides from Portulaca oleracea: Isolation, Structure, and DPPH Radical Scavenging Activity

Jiao, Ze-Zhao, Yue, Su, Sun, Hong-Xiang, Jin, Tian-Yun, Wang, Hai-Na, Zhu, Rong-Xiu, Xiang, Lan
Journal of natural products 2015 v.78 no.11 pp. 2588-2597
2,2-diphenyl-1-picrylhydrazyl, Portulaca oleracea, amides, ammonia, antioxidant activity, antioxidants, ascorbic acid, chromatography, glucosides, median effective concentration, medicinal plants, polyamides, spectroscopy, structure-activity relationships
A polyamide column chromatography method using an aqueous ammonia mobile phase was developed for large-scale accumulation of water-soluble indoline amide glucosides from a medicinal plant, Portulaca oleracea. Ten new [oleraceins H, I, K, L, N, O, P, Q, R, S (1–10)] and four known [oleraceins A–D (11–14)] indoline amide glucosides were further purified and structurally characterized by various chromatographic and spectroscopic methods. The DPPH radical scavenging activities of oleraceins K (5) and L (6), with EC₅₀ values of 15.30 and 16.13 μM, respectively, were twice that of a natural antioxidant, vitamin C; the EC₅₀ values of the 12 other indoline amides, which ranged from 29.05 to 43.52 μM, were similar to that of vitamin C. Structure–activity relationships indicated that the DPPH radical scavenging activities of these indoline amides correlate with the numbers and positions of the phenolic hydroxy groups.