Polyphenolic antioxidants from Sapotaceae fruits.

摘要

Tropical edible plants are rich sources of phytochemical antioxidants. In this study, forty-nine tropical edible plants were selected to undergo screening for antioxidant activity using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical assay. Among them, thirty-six displayed antioxidant activity. Of these thirty-six plants with antioxidant activity, four were from the Sapotaceae family, namely, Manilkara zapota, Pouteria campechiana , Pouteria sapota, and Pouteria viridis , these plants were selected to undergo activity-guided fractionation and isolation to study their antioxidant constituents.; Activity-guided fractionation of a methanol (MeOH) extract from the fruit of Manilkara zapota cv. Tikal resulted in the isolation of two new antioxidants, methyl 4-O-galloylchlorogenate and 4-O-galloylchlorogenic acid, along with eight known polyphenolic antioxidants, namely, methyl chlorogenate, dihydromyricetin, quercitrin, myricitrin, (+)-catechin, (-)-epicatechin, (+)-gallocatechin, and gallic acid. Of the ten polyphenols, methyl 4-O-galloylchlorogenate showed the highest antioxidant activity in the DPPH assay with IC50 = 12.9 muM, and displayed cytotoxicity to the HCT-116 and SW-480 human colon cancer cell lines with IC50 values of 190 and 160 muM, respectively. With an IC50 of 23.5 muM, 4-O-galloylchlorogenic acid showed a high antioxidant activity in the DPPH assay, and displayed cytotoxicity to the HCT-116 and SW-480 human colon cancer cell lines with IC50 values of 154 and 134 muM, respectively.; Fresh fruits of Pouteria campechiana, Pouteria sapota, and Pouteria viridis, were extracted and activity-guided fractionations of the corresponding extracts were performed to identify the antioxidant constituents. Seven polyphenolic antioxidants, gallic acid, (+)-gallocatechin, (+)-catechin, (-)-epicatechin, dihydromyricetin, (+)-catechin-3-O-gallate, and myricitrin, were isolated and identified. Extracts of these three Pouteria fruits were analyzed by a selected ion monitoring liquid chromatography-mass spectrometry method to quantify their polyphenolic antioxidants. The highest level of the seven measured polyphenols was found in P. sapota, the second highest in P. viridis, and the lowest in P. campechiana . The levels of the seven polyphenols corresponded with the results of the DPPH assay, where P. sapota had the highest antioxidant activity, P. viridis the second highest, and P. campechiana the lowest.; The results of this study may provide additional nutrition information for little used tropical fruits grown commercially in the US, as well as in other subtropical and tropical areas. These fruits may be a good source of potential chemopreventive agents.