Influence of various cooking treatments and extraction solvents on bioactive compounds and antioxidant capacities of bottle gourd ( Lagenaria siceraria ) fruit in India

Bottle gourd is a good source of health-beneficial bioactive substances. This research aimed at evaluating the effect of different cooking methods (pressure cooking, microwaving, and frying) and extraction solvents (methanol, ethanol and butanol) on bottle gourd fruit phenolic compounds and antioxidant capacity. The quantitative estimation of polyphenolic compounds, flavonoids and tannins was estimated by spectrophotometric methods. The antioxidative properties were evaluated using ferric thiocyanate (FTC), thiobarbituric acid (TBA), ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) tests using the standard methods. Moreover, quantification of individual polyphenols was carried out by high-performance thin layer chromatography (HPTLC) technique. Frying and pressure-cooking thermal treatments were observed to be the best methods for retaining bioactive molecules. When compared to the raw counterpart, the retention level of total phenol content (TPC) in pressure cooked and fried samples was 23.8% and 13.3%, respectively. Similarly, antioxidant capacity in terms of FRAP was observed to increase by 47.26% after pressure cooking and 28.50% after microwave cooking in respect to the raw sample. The HPTLC results showed that this fruit has high antioxidant capacity and is rich in phenolic acid [gallic(17.83 mg g −1 dwb), p-coumaric (6.70 mg g −1 dwb)and vanillic (60.66 mg g −1 dwb] and flavonoids [quercetin (24.64 mg g −1 dwb) and myrecetin (20.73 mg g −1 dwb].The chromatography indicated destruction and transformation of new phenolic compounds due to heat treatments. The correlation analysis revealed that flavonoids were much more responsible for their antioxidant activity. Cooking methods and extraction solvents affected the retention and recovery of polyphenolic compounds available in bottle gourd fruit . These findings offer valuable information for optimizing cooking techniques to preserve and enhance the nutritional and antioxidant properties of bottle gourd, making it a valuable fruit for a healthy diet. Pressure cooking could be the most suitable cooking treatment as far as retention of bioactive compounds like phenolic acids is concerned. Graphical Abstract