Bioactive condensed tannins from bark: chemical properties, enzyme inhibition and anti-plant-viral activities.
Nondialysable, highly condensed, procyanidin type tannins were isolated from constituents in the barks of Cedrus deodara (CDL), Prunus yedoensis (PYM), Thujopsis dolabrata (TDS), Pterocarpus indicus (PI), Cryptomeria japonica (CJD) and Pinus thunbergii (PTP) as partially purified, brownish powders. These compounds differed primarily in av. MW (PI: 20 000, CDL: 10 000, PYM: 8000 and TDS: 5000) and showed >1000 times stronger enzyme-inhibitory activity (plasmin (ED50: 0.05-0.4 µsmallcap˜M), thrombin (0.02-0.2 µsmallcap˜M), papain (0.08-0.6 µsmallcap˜M), trypsin (0.25-2.0 µsmallcap˜M)) than (-)-epicatechin on a molar-ratio basis. The mode of inhibition of CDL was determined to be noncompetitive-uncompetitive on both plasmin and papain. In preliminary anti-plant-viral bioassay, CDL showed a protective effect (93%) when applied to glove amaranth [Gomphrena globosa] at 1000 p.p.m. before inoculation with potato X potexvirus and a therapeutic effect (80%) against potato X potexvirus, tobacco mosaic tobamovirus and cucumber green mottle mosaic tobamovirus when applied after inoculation of tomato, tomato and cucumber plants, respectively.