Efficacy of Neem Kernel Bioactives Extracted using Supercritical Fluid Carbon Dioxide on Selected Dermatophytes and Foodborne Pathogens

Abstract

Neem seed kernel was subjected to supercritical fluid carbon dioxide (SCF) process and evaluated for the inhibition of selected dermatophytes such as Candida albicans, Candida tropicalis, Candida parapsilosis, Trichophyton rubrum, Trichophyton mentagrophytes. The extraction was carried out by SCF-CO2 at 300 bar 50 °C with and without entrainer (30 % methanol and acidified methanol). Results showed that the inhibition of the growth of all the dermatophytes is maximum in the extract obtained at 300 bar 50 °C with methanol (SCF-Me) followed by 300 bar 50 °C without methanol (SCF). The acidified SCF (SCF-MeA) extract did not show any remarkable inhibition. Of the dermatophytes, SCF-Me showed the inhibition against Candida parapsilosis of 18.46±0.25 mm compared to Candida albicans 16±0.26 mm, whereas the methanol control exhibited 10±0.3 mm inhibition. Out of the two fungal organisms, SCF-Me inhibited the growth of Trichophyton rubrum and Trichophyton mentagrophytes at 21.53±0.23 mm and 18.1±0.1 mm respectively. The extracts were also evaluated for its inhibition against the foodborne pathogens (bacteria, fungi, and yeast). The SCF-Me extract showed maximum inhibition against Pseudomonus aeroginosa (27.26±0.25) compared to Bacillus subtilis (24.36±0.35) at the concentration of 70mg. In fungus, Aspergillus ochraceus (16.7±0.60) was maximum when compared to Aspergillus niger (15.2±0.43) and yeast exhibited the inhibition of 15.93±0.20 at the concentration of 80mg. The dermatophytic and antimicrobial activity of the SCF-Me extract is due to the presence of higher amount of triterpenoinds such as Azadirachtin (50.7 %), 6-deacetyl nimbin (0.14 %), Nimbin (0.08 %), Salannin (1.83 %) and Epoxy azadiradione (1.58 %) which were confirmed by liquid chromatography and mass spectroscopy (LC-MS).