Variation of bioactive compounds and antioxidant activity of carambola (Averrhoa carambola L.) fruit at different ripening stages

• Bioactive compounds and antioxidant activity of carambola fruit at 5 ripening stages were analyzed by multivariate analysis.
• Harvesting carambola fruit must be done at specific time to get optimum level of bioactive compounds and antioxidant benefit.
• Bioactive compounds profile could be potential metabolite marker to determine carambola fruit ripening stages.

The variations in bioactive compounds and antioxidant activity of carambola (cv. B17) fruit at different ripening stages were investigated. The carambola fruit was harvested from week 9 until week 13. Ascorbic acid (AA), total phenolic content (TPC), total flavonoids content (TFC), total carotenoids content (TCC), β-carotene, tocopherol homologues (α, β, γ and δ) and sugar composition (sucrose, glucose and fructose) were analyzed for each sampling week. Antioxidant activity was measured with 2,2-diphenyl-1-picrylhydrazil(DPPH) and β-carotene/linoleic acid model(BCLAM) assays. The results showed that AA, TCC and sugar composition were significantly (P < 0.05) increased while TPC, TFC and β-carotene showed reversed trends as ripening process was in progressed. Interestingly, the tocopherol compounds varied differently with contribution of α- and β-tocopherols highest on week 12 and then decreased on week 13 but γ- and δ-tocopherols were constantly decreased during ripening. Meanwhile, antioxidant activities for both assays were significantly (P < 0.05) decreased. Multivariate analysis revealed a notable variation of tested attributes among the ripening stages. Bioactive compounds such as TPC, TFC, β-carotene, γ- and δ-tocopherol were found to be dominant in unripe fruit while those of sugar (sucrose, glucose and fructose), TCC, α- and β-tocopherol were prominent in the ripe fruit. The findings of this study advocate harvesting of carambola fruit at an appropriate stage to get maximum nutritional benefits.