Novel findings on the bioactivities of black ginger of Vietnam and optimization of its extraction using response surface methodology

The present study aimed to evaluate the antioxidant activity and antithrombotic effect of the n-hexane extract from rhizomes Distichochlamys citrea (DC-R), an endemic ginger species of Vietnam. Results showed that DC-R expressed a more potent antioxidative effect against ABTS than DPPH radical (p < 0.05). DC-R contained a total phenolic content of 3.41 g GAE/100 g and a total flavonoid content of 18.33 g QE/100 g of the dried extract. At concentrations of 1, 2 and 4 mg/mL, DC-R reduced the percentage of platelet aggregation triggered by ADP, collagen and ristocetin in a dose-dependent manner (Pearson’s correlation, r > 0.95, p < 0.05). DC-R also exhibited anticoagulant activity by significantly prolonging the activated prothrombin time (APTT) at all concentrations tested (p < 0.05 compared to DMSO 0.1%). GC–MS revealed 41 volatile components in DC-R, in which several compounds were firmly bound to receptors COX-1 and P2Y12 of the platelet aggregation and factors X and II of the blood coagulation cascades. Using response surface methodology with central composition design, the extraction yield of DC-R reached the highest value (1.011 ± 0.008%) at optimized conditions: liquid/ solid ratio 13.5 mL/g, ultrasonic power level 80%, extraction time 30 min, and extraction temperature 34 °C.