Antioxidant properties of fractions for unripe fruits of Capsicum annuum L. Var. conoides

Background: Capsicum plant, especially for C. annuum, is an abundant resource for bioactive anti-oxidants, but few studies have examined the unripe fruit part of the Capsicum plant. Objective: MeOH extract of unripe fruits of C. annuum L. var. conoides (UFCA) was chromatographed over a silica gel column using a gradient of CH₂Cl₂/MeOH as eluent to produce 9 fractions. Antioxidant activities are evaluated along with cell viabilities of 9 fractions of UFCA. Method: The antioxidant properties were analyzed in terms of total phenol content (TPC), total flavonoid content (TFC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, 2,2-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) radical scavenging, ferric reducing, and ferrous ion-chelating ability. The cell viability of human oral cancer cells (Ca9-22) was measured by 3-(4,5-dimethylthiazol-2-yl)-(3-carboxymethoxyphenyl)-2-(4-sulphophenyl)-2H-tetrazolium (MTS) assay. Results: Except for TFC, fractions (Frs.) 1 and 2 showed the lowest level of these antioxidant properties. Frs. 3 to 9 showed dose-responsive induction for antioxidant effects. Fr. 8 and Fr. 5 respectively showed the highest levels of TPC and TFC for 1162 ± 11 gallic acid equivalents (GAE) (mg)/UFCA (g) and 1295 ± 32 quercetin equivalents (QCE) (mg)/UFCA (g). The cell viability of Fr. 3 was moderately decreased (78.2%) while those of Frs. 4, 5, and 9 were dramatically decreased (55.6, 57.8, and 46.8%, respectively) in oral cancer Ca9-22 cells. UFCA-derived 14 compounds/mixtures derived from Frs. 1, 2, 3, 4, and 8 displayed differential antioxidant performance for these analyses. Conclusion: Taken together, fractions of UFCA displayed diverse antioxidant and anticancer effects for oral cancer cells. Some fractions of UFCA may be potent natural antioxidant supplements for antioral cancer cell treatment.