Improving phenolic antioxidants in Illicium griffithii fruit through optimizing subcritical water extraction method

The Illicium griffithii is a medicinal and aromatic plant species found in the temperate broadleaf forests of the Northeast region of India. The fruit of this species has been traditionally used in ethnomedicine and holds significant economic potential. This study aimed to determine the optimal conditions for better recovery of phenolic antioxidants from Illicium griffithii fruit using subcritical water extraction. Box-Behnken Design (BBD) was used to assess the impact of temperature (100-220 °C), pressure (30-90 bar), and time (10-50 min) on the extraction yield of phenolic antioxidants. Total phenolic content (TPC) varied from 15.60 to 30.91 mg GAE/g dw; whereas total flavonoid content (TFC) from 1.48 to 2.44 mg QE/g dw; while DPPH from 19.23 to 24.70 µg AAE/g dw; and ABTS from 16.36 to 17.92 µg AAE/g dw. Under the optimal conditions (161.32 °C, 45 bar, and 30 min), the phytochemical (TPC- 30.91 ± 0.07 mg GAE/g dw; TFC- 2.07 ± 0.02 mg QE/g dw) recovery echoed the scavenging activities (DPPH - 23.27 ± 0.13 µg AAE/g dw; ABTS- 17.82 ± 0.03 µg AAE/g dw). The phenolic profile revealed the improved concentration (1.60 to 9.77 m/g), with predominant phenolic compounds such as gallic acid (9.77 mg/g), catechin (8.84 mg/g) and p-hydroxybenzoic acid (4.06 mg/g). Among the different process parameters, temperature has significantly influenced the recovery of the phenolic antioxidants in Illicium griffithii fruit. ATR-FTIR spectra confirmed the occurrence of alcoholic, phenolic, and aromatic compounds in the SWE extract, with variations in temperature and pressure notably influencing the aromatic and phenolic functional groups. The results show better efficacy of SWE process as compared to other processes in terms of higher yield, reduced time, higher bioactivity, etc.