Characterization and antibacterial properties of oak tasar and mulberry silkworm pupae oils

Abstract

Current study provides a valuable insight into physical, thermal, and antibacterial studies of oak tasar pupae oil (OTPO) and mulberry silkworm pupae oil (MSPO). It was observed that both OTPO and MSPO showed comparable melting ranges which were -105°C to -70°C for OTPO and -96°C to -70°C for MSPO. However, this also shows that OTPO solidifies at lower temperatures than MSPO. The viscosity of OTPO was observed as 26.16 cP, whereas, for MSPO it was 25.60 cP. The colour of the OTPO appeared as brown and yellow for MSPO which corresponds to the values 18Y + 2.1 R and 14Y + 1.0 R displayed through the tintometer, respectively. The specific gravity values OTPO and MSPO were 0.863 ± 0.0016 and 0.910± 0.001 respectively. The antibacterial activity of the oil samples was evaluated against Streptococcus pyogenes (MTCC733) and Salmonella typhi (MTCC442). Both OTPO and MSPO emphasized significant bactericidal abilities against the selected bacterial strains. OTPO exhibited higher antibacterial activity on gram-negative S. typhi of 15.33 ±1.15mm at 70µL. Whereas, MSPO exhibited a maximum zone of inhibition of 13 ± 1mm at 70µL on gram-positive S. pyogenes. Further, at 20µL, MSPO showed an inhibition of 9 ± 0mm against S. pyogenes, while OTPO showed no activity against any of the strains. Furthermore, at 50µL, the zone of inhibition of 9.67 ± 0.58mm was observed for both OTPO and MSPO against S. pyogenes. Although, at the same concentration12.67 ± 1.15mm zone of inhibition was measured for OTPO and no activity for MSPO was obtained for S. typhi. The results showed significant antibacterial activity, for OTPO, which exhibited a maximum inhibition zone of 15.33 ± 1.15mm against S. typhi.