Proanthocyanidin Oligomers Isolated from Salacia reticulata leaves potently Inhibit Pancreatic Lipase Activity

Abstract

The pancreatic lipase inhibitory (PLI) activity of leaf extracts (aqueous, 60 and 99.8 (v/v)% EtOH) of Salacia reticulata Wight, referred to "Kothala himbutu" (KT) in Singhalese, was compared with that of KT stem extracts. Evaporated residue contents and PLI activity of each leaf extract were higher than those of each stem extract, respectively. Among the extracts, the 60% EtOH leaf extract showed the most potent PLI activity. The 60% EtOH leaf extract was separated by a Diaion HP20/water-acetone system and furthermore the most potent fraction by a Sephadex LH20/water-ethanol-acetone system. The 60% acetone fraction from the LH20/water-ethanol-acetone system had the most potent PLI activity (IC(50) value; 15 ppm). The active compounds in the active fraction of KT leaves were most likely a polyphenol, as assessed by the Folin-Ciocalteu method. Based on these spectroscopic and chemical examinations, the active fraction was shown to be proanthocyanidin oligomers composed of epigallocatechin, epicathechin, and epiafzelechin as main constituents. The degree of polymerization was estimated to be about 5 from the ratio of the peak area of the thio ethers/flavan-3-ols at 230 nm. This was consistent with the results of matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) MS, which showed the [M+Na](+) peaks corresponding to trimers-octamers. From the average molecular weight and IC(50) value of the active compounds estimated on these results, the active compounds from the KT leaf extract were one of the stronger effective lipid-lowering therapeutic agent, of which PLI activity (μM/L) was almost the same as epigallocatechin gallate. Proanthocyanidin oligomers isolated from Salacia reticulata, referred to "Kothala himbutu" (KT) in Singhalese, leaves was proved to potently inhibit pancreatic lipase activity. After confirming in vivo examination, healthy foods, teas, and liquors containing the extracts of KT leaves are expected to be on market.