Extraction of Swietenia macrophylla seed by using microwave assisted extraction technique and the characterisation of its phytochemical properties

Abstract

Swietenia macrophylla (S.macrophylla) or commonly known as Tunjuk Langit in Malaysia has been used as traditional remedy for diseases treatment as the seeds of S. macrophylla have been examined for its anti-inflammatory, antimutagenecity, and anti-tumour activities. The objectives of this research are to optimise the extraction of the S. macrophylla seed oil by using microwave assisted extraction (MAE) and to evaluate physicochemical and biological properties of the extracted S. macrophylla seed oil. MAE provides process acceleration and higher extraction yield compared to conventional extraction. The operating parameters were optimized by response surface methodology using design expert version 6 to obtain optimum yield of S. macrophylla seed oil. Properties of S. macrophylla seed oil were characterised by using total phenolic content (TPC), antioxidant properties via DPPH (2,2-diphenyl-1-picrilhydrazyl) and ABTS (2,2'-azino-bis-(3-ethylbenzothiazoline-6- sulphonic acid)) free radical scavenging method, the anti-diabetic activity via aglucosidase and a-amylase inhibition assays and the anti-microbial activity via agar disk-diffusion method. Gas chromatography-mass spectrometry (GC-MS) was used to analyse the fatty acid composition in the seed oil. The result showed that 43.69 ± 0.092 w/w % oil yield was obtained at optimal condition of 6 min irradiation time, solvent-to-solid ratio of 26 mL solvent/g solid and 460 W microwave power. The seed oil extracted by using MAE exhibited the highest TPC concentration, the best DPPH and ABTS inhibition compared to supercritical carbon dioxide extraction (SCCO2) and soxhlet extraction (SE) method. S. macrophylla seed oil demonstrated potent inhibition on a-amylase but weak inhibition towards a-glucosidase enzyme. S. macrophylla seed oil was found to have excellent inhibition zone towards Escherichia coli and Bacillus subtilis. Result from GC-MS analysis showed that the S. macrophylla seed oil was composed of fatty acids including linoleic (32.1%), oleic (57.3%) and palmitic (10.6%). These findings proved that S. macrophylla seed oil extracted using MAE could provide better quantity and quality of oil in shorter time compared to SC-CO2 and SE methods.