A major development over the past two decades has been the realization that free radical induced lipid peroxidation and DNA damage are associated with major health problems, e.g. cancer and ageing. Plant-derived antioxidants are increasingly found beneficial in protecting against these diseases. Celtis australis L. and Celtis occidentalis L. are two plants that have a variety of uses in folk medicine but have not been evaluated before for their antioxidant and cytotoxic properties. Therefore, the extracts of both plants’ leaves were investigated for these activities, as well as isolation of the bioactive compounds responsible for the activities. Molecular structures of the compounds were elucidated by UV, HRESIMS, 1D (1H and 13C) and 2D (1H-13C HSQC and 1H-13C HMBC) NMR analyses. The ethanolic and aqueous extracts, n-butanol fractions and the isolated major compound were tested for their antioxidant activity using DPPH radical scavenging assay, xanthine oxidase-induced generation of superoxide radical and lipid peroxidation assay by thiobarbituric acid-reactive substances (TBARS) method using rat tissue homogenates. Cytotoxic activities were studied using standard MTT assay. A novel flavonoid C-triglycoside, 4‴-α-rhamnopyranosyl-2″-O-β-d-galactopyranosylvitexin, was isolated from both plants’ leaves, together with seven known flavonoids. The n-butanol fractions and the major compound 2″-O-β-galactopyranosylvitexin showed significant antioxidant activities, more pronounced than the tested standards BHT and dl-α-tocopherol in most tests. All extracts showed variable cytotoxic activities. This study provides strong evidence for the antioxidant and cytotoxic activities of the extracts of Celtis australis L. and Celtis occidentalis L. leaves, which were attributed to the polar n-butanol fractions and the major isolated flavonoid 2″-galactosylvitexin.

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A new flavonoid glycoside, 5,7,4´-trihydroxy-3,6-dimethoxyflavone-3´-O-β-D-xylopyranoside (axillarin-3´-O-β-Dxylopyranoside), was isolated from the ethyl acetate fraction of the ethanolic extract of Platanus orientalis L. leaves, along with nine known flavonoid aglycones and glycosides, a phenolic acid and a phenolic acid derivative. Their structures were established on the basis of detailed spectral analysis. The total ethanolic, aqueous and ethyl acetate extracts of the leaves were tested for antihepatotoxic, antioxidant and cytotoxic activities. The extracts were found to be effective in protection against CCl 4 liver injury by significantly lowering alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) levels. The extracts also significantly restored depleted levels of glutathione, indicating a strong antioxidant activity, while they showed variable cytotoxic activity.

Two novel acylated flavonol glycosides were isolated from the n-butanol fraction of the ethanolic extract of Platanus orientalis L. leaves. They were identified as kaempferol-3-O-(2´´´-p-E-coumaroylrhamnosyl)(1´´´→6´´)-[β-D-glucopyranosyl-(1´´´´→2´´)-β-D-glucopyranoside]-7-O-α-L-rhamnopyranoside, and quercetin-3-O-(2´´´-p-E-coumaroylrhamnosyl)(1´´´→6´´)-[β-D-glucopyranosyl-(1´´´´→2´´)-β-D-glucopyranoside]-7-O-α-L-rhamnopyranoside. Their structures were established on the basis of detailed spectral analysis.