SUPERCRITICAL CARBON DIOXIDE EXTRACTION OF MELATONIN FROM BRASSICA CAMPESTRIS: IN VITRO ANTIOXIDANT, HYPOCHOLESTEROLEMIC AND HYPOGLYCAEMIC ACTIVITIES OF THE EXTRACTS

Brassica campestris Linn. (yellow mustard), a common Indian condiment, possesses melatonin as an important antioxidant. Optimization of supercritical carbon dioxide extraction (SC-CO₂) process parameters was conducted to obtain an extract having the best combination of yield of melatonin and maximum in vitro hypoglycaemic and hypocholesterolemic activities, along with a desirable balance of ω6 to ω3 fatty acids. A full factorial design and response surface methodology were employed for process optimization. Melatonin content of the extracts was obtained by high performance liquid chromatography and by liquid chromatography-mass spectrometry. The optimized extraction conditions were obtained at 300 bar, 50 °C for 120 min. This extract exhibited highest content of melatonin (660.72±41.05 ng/g of dry mustard powder), maximum in vitro hypocholesterolemic (60.11±3.89%) and hypoglycaemic (59.70±2.67µg/ml) activities and possessed minimum ω6 to ω3 (1.29) ratio with minimum erucic acid content (2.00±0.20 g/100g of fatty acid). The  electron  paramagnetic  resonance  spectroscopy of  the  extract  (0.10±0.001  g/ml)  showed  72.10±4.01%  scavenging  activity  of DPPH radicals, establishing its strong antioxidant potency. A new Chrastil equation was developed to compute solubility of melatonin in SC-CO₂ under different extraction conditions. The SC-CO₂ extract of yellow mustard seeds could have promising use as a natural source of melatonin as well as of balanced ω6 to ω3 fatty acids.