Enzyme mediated-transesterification of verbascoside and evaluation of antifungal activity of synthesised compounds

Enzymatic acylation of verbascoside, a polyhydroxylated natural product, has been reported in this study using five different commercial lipases and taking p-nitrophenyl alkanoates as acyl donors. Out of these enzymes, the immobilised Candida antarctica lipase B was found as the enzyme of choice. Mono- and di-acylated products were formed, with mono as major product indicating high regioselective nature of such transformations. A series of acyl esters of verbascoside have been synthesised by this enzymatic transesterification methodology. The lipophilicity of the synthesised analogues was also checked. The analogues were further subjected to synergistic antifungal activity with amphotericin B (AmB) against Candida albicans. Fourfold reduction in minimum inhibitory concentration of AmB was observed with few synthesised analogues such as verbascoside 400-octanoate (3b), verbascoside 400- palmitate (3d) and verbascoside 400,40 -dipalmitate (4d) at a concentration of 0.5mg/mL.Integrative Medicine (IIIM) and University of Pretoria.http://www.tandfonline.com/loi/gnpl20hb2017Chemistr

Effects of drying methods on the characteristics of rambutan (nephelium lappaceum l.) seed fat: An optimisation approach

The pre-treatment of oilseeds prior to extraction process may affect oil yield and quality. The aim of this study was to investigate the effects of two drying methods on rambutan seed fat (RSF) yield and their oxidative stability, physicochemical properties, and crystal morphology. Response surface methodology (RSM) was used in the optimisation and investigation of the effects of three process conditions: seed weight (g), extraction time (min), and solvent volume (ml) on RSF yield. Under optimal conditions, a maximum RSF yield of 44.14% was obtained. The differences between RSF pre-treated with oven-drying and RSF with freeze-drying methods in slip melting point (38.3◦C to 39.7◦C), free fatty acid (3.13 to 3.50 mg KOH/g fat), peroxide value (1.04 to 1.67 meq of O2/kg of fat), p-anisidine value (1.10 to 1.56), and total oxidation value (4.21 to 5.67) were significant (p < 0.05). Both fats showed needle-like shaped crystals. Our results provide useful information in the pre-treatment of RSF,which has potential to be used as blending component with palm oil for cocoa butter equivalent formulation in chocolate and confectionery industries