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  • Author or Editor: Rajesh Singh x
  • Chemistry and Chemical Engineering x
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A high-performance thin-layer chromatography (HPTLC) method has been developed and validated for the quantification of two bioactive lupane triterpenoids, namely, lupeol and betulin from Diospyros melanoxyon stem bark. Chromatographic separation was achieved on aluminium foil-backed HPTLC plates using ethyl acetate-hexane (1.8:8.2, v/v) as mobile phase. The compounds were quantified at their wave length of maximum absorbance in the range of 100–500 ng per spot. The instrumental precision was 0.82% and 1.07% (CV) and the repeatability of the method was 1.33% and 1.17% (CV), respectively, for lupeol and betulin. The minimum detectable amount was found to be 40 and 50 ng per spot for lupeol and betulin, respectively. The linear regression analysis data for the calibration plots showed a good linear relationship with r 2 = 0.9996 for lupeol and 0.9997 for betulin. The method was validated for precision, recovery, and repeatability as per the International Conference on Harmonization guidelines. The developed HPTLC method is very accurate and precise, and has been successfully applied for the assay of these bioactive molecules in D. melanoxylon stem bark.

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An important bioactive molecule, ursolic acid was isolated from the leaves of Diospyros melanoxylon and characterized with help of physical and spectroscopic data viz. m. p, IR, 1H, and 13C NMR. A high-performance thin-layer chromatography method has also been developed and validated for its quantification in D. melanoxylon leaves. The high-performance thin-layer chromatography analysis was performed on high performance thin-layer chromatography plates using chloroform-methanol (9.5:0.5, v/v) as mobile phase. The compound was quantified at 540 nm after derivatzation with sulphuric acid reagent. The sensitivity of the method with respect to limit of detection and limit of quantification were found to be 20 and 40 ng per spot. The response was obtained as a linear function of peak area and concentration in the range of 50 to 450 ng per spot with correlation coefficient of r 2 = 0.9998. The method showed excellent accuracy greater than 97.54% with acceptable precession and was successfully validated according to International Conference of Harmonization protocols. Antimicrobial screenings of ursolic acid revealed potent activity against two Gram-positive bacteria viz. Staphylococcus aureus and Enterococcus faecalis and three fungal starins viz. Aspergillus niger, Candida tropicalis, and Candida albicans.

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The thermal degradation of graft copolymers of both polysaccharides (guar gum and xanthan gum) showed gradual decrease in mass loss. Pure guar gum degraded about 95% but pure xanthan gum degraded about 76% up to 1173.15 K, while graft copolymers of guar gum and xanthan gum degraded only 65–76% up to 1173.15 K. Acrylic acid grafted guar gum and xanthan gum showing two-step degradation with formation of anhydride and ketonic linkage during heating, same pattern of degradation was found for xanthan gum-g-methacrylic acid. Guar gum-g-acrylamide degraded in single step and xanthan gum-g-acrylamide started to degrade above 448.15 K and it is a two-stage process and imparts thermal stability due to the formation of imide linkage with evolution NH3. Guar gum-g-methacrylamide degraded in three steps due to the loss of NH3 and CO2 successively. 4-vinyl pyridine grafted both polysaccharides show single step degradation due to loss of pyridine pendent. N-vinyl formamide grafted guar gum and xanthan gum started to degrade at about 427.15 K, showed two-stage degradation process with the evolution of CO and NH3 molecules while guar gum-g-(N-vinyl-2-pyrrolidone) degraded into two steps by the loss of pyrrolidone nucleus. Gum-g-2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) showed two-step degradation processes in two successive degradation steps, while xanthan gum-g-AMPS has started degradation at about 427.15 K and completed in five degradation steps. Overall, it was found that the grafted polysaccharides are thermally more stable than pure polysaccharides.

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