Antimicrobial constituents of Thompson seedless raisins (Vitis vinifera) against selected oral pathogens

As a part of a project directed toward the discovery of oral antimicrobial compounds from plants, eight known compounds, oleanolic acid (1), oleanolic aldehyde (2), linoleic acid (3), linolenic acid (4), betulin (5), betulinic acid (6), 5-(hydroxymethyl)-2-furfural (7), and beta-sitosterol were isolated from an hexane-soluble partition of a methanol extract of Thompson seedless raisins (Vitis vinifera). From an EtOAc-soluble partition rutin (8) and P-sitosterol glycoside were isolated. In an attempt to increase the resultant antimicrobial activity of oleanolic acid (1), a series of acylation and etherification reactions were performed on oleanolic acid to obtain derivatives 1a-1f. All the compounds isolated and the derivatives 1a-1f were evaluated for their antimicrobial activity against two oral pathogens, Streptococcus mutans and Porphyromonas gingivalis associated with caries and periodontal disease, respectively. Compounds 1, 2, 7 and 1f inhibited the growth of the test bacteria with concentrations ranging from 3.9 to 500 mu g/mL. Derivative 1f showed greatly enhanced antimicrobial activity when compared with oleanolic acid (1). Published by Elsevier B.V. on behalf of Phytochemical Society of Europe.