Supercritical CO2 extraction of functional compounds from Spirulina and their biological activity

Supercritical carbon dioxide (SCCO2) extraction and fractionation of Spirulina platensis was carried out to obtain functional compounds with antioxidant, antimicrobial and enzyme inhibitory activities. Extraction of SCCO2 was carried out using 200 g of Spirulina powder at 40 ºC under 120 bar pressure with CO2 flow rate of 1.2 kg h−1. SCCO2 fraction obtained was further treated with hexane and ethyl acetate to identify its components. Individual components were identified by comparing mass spectra of samples with standard data and retention indices (RI) of C5–C20 n-alkanes mixture using the kovat index formula. The phenolic and flavonoid content of the SCCO2 extract was found to be 0.34 ± 0.01 g/100 g and 0.12 ± 0.01 g/100 g respectively. The SCCO2 extract had antioxidant activity with IC50 value of 109.6 ± 3.0 μg mL−1 for DPPH (2,2-Diphenyl-1-picryl hydrazyl radical), IC50 value of 81.66 ± 2.5 μg mL−1 for reducing power and IC50 value of 112.70 ± 0.8 μg mL−1 for hydroxyl radical scavenging activity. Further, antioxidant activity study on oxidative induced DNA damage was analysed to elucidate the positive role of SCCO2 extract. SCCO2 extracts showed high antimicrobial activity against Gram-positive bacteria (Staphylococcus aureus FRI 722 and Bacillus cereus F 4810) compared to that of Gram negative bacteria (Escherichia coli MTCC 108 and Yersinia enterocolitica MTCC 859). The SCCO2 extract exhibited inhibitory activity on both Angiotensin-1 converting enzyme and α-glucosidase with IC50 values of 274 ± 1.0 μg mL−1 and 307 ± 2.0 μg mL−1 respectively.