Proximate, mineral, chemical composition, antioxidant and antimicrobial potential of dropped fruits of Citrus reticulata Blanco

The naturally dropped immature fruits of Citrus reticulata Blanco are generally discarded as waste but they have enormous potential to be used as nutraceuticals. This work was planned to evaluate the proximate, mineral composition, total phenolic and flavonoid content, antioxidant and antimicrobial potential of dropped fruits of C. reticulata Blanco. Proximate analysis showed them as a good source of carbohydrates and proteins. Mineral analysis revealed the presence of K, Mg, P, Ca and Na as macronutrients and Fe, B, Mn and Ni as micronutrients. The total phenolic and flavonoid content of methanol extract and its fractions ranged between 2.47 and 51.36 mg gallic acid equivalent g−1 DW and 11.47–86.50 mg quercetin equivalent g−1 DW respectively. The antioxidant potential of dropped Citrus fruits was determined by two in vitro (DPPH and ABTS) assays and various enzymatic antioxidant assays. Maximum antioxidant potential was shown by ethyl acetate fraction having the least IC50 value of 21.20 and 78.5 mg/g in DPPH and ABTS radical scavenging assays respectively. In the antioxidant enzymatic assay, catalase exhibited maximum activity with 18.46 U min−1 g−1 FW followed by superoxide dismutase (12.87 U min−1 g−1 FW), ascorbate peroxidase (3.82 U min−1 g−1 FW) and peroxidase (0.2112.87 U min−1 g−1 FW). Maximum antibacterial activity was shown by methanol extract having the least MIC values against Escherichia coli (186 μg ml−1), Yersinia enterocolitica (190.5 μg ml−1), Staphylococcus aureus (135.5 μg ml−1) and Bacillus sp. (85 μg ml−1). GC–MS analysis of the methanolic extract revealed the presence of flavonoids, fatty acid derivatives, phenols, terpenoids, steroids, organic acid and amino acid.