Rapid estimation of piperine in black pepper: Exploration of Raman spectroscopy.

INTRODUCTION: The major chemical marker of black pepper (Piper nigrum L) is piperine and its estimation is extremely important for quality assessment of black pepper. The methods for piperine quantification, to date, are laboratory based and use high end instruments like chromatographs, which require tedious sample processing and cause sample destruction. OBJECTIVES: In this article, we present a simple, rapid and green analytical method based on Raman spectroscopy for the quantitative assessment of piperine. MATERIAL AND METHODS: To assess the potential of the technique, we report the complete vibrational characterisation of the piperine with density functional theory (DFT) calculations. RESULTS: The theoretical peaks were obtained at 1097 cm-1 , 1388 cm-1 , 1528 cm-1 , 1578 cm-1 , and at 1627 cm-1 , and this result was verified in a Raman spectrometer followed by a preliminary experiment. Twenty black pepper samples were analysed using high-performance liquid chromatography (HPLC) and used as reference data for Raman analysis. The Raman shift spectra were analysed using partial least squares (PLS) and good prediction accuracy with correlation coefficient of prediction (Rp2 ) = 0.93, root mean square error of prediction (RMSEP) = 0.13 and residual prediction deviation (RPD) = 3.9 obtained. CONCLUSIONS: The results demonstrate the efficacy of the Raman technique for the estimation of piperine in the dry fruit of Piper nigrum.

LC-QTOF-MS-based metabolite profiling and evaluation of α-glucosidase inhibitory kinetics of Coccinia grandis fruit.

Coccinia grandis is an important food crop of the Cucurbitaceae family, widely used for culinary purposes in India. It is reported to possess hypoglycemic, hypolipidemic and antioxidant activities. The current study was aimed to explore the inhibition kinetics as well as major constituents of the active fraction of C. grandis against α-glucosidase. The kinetic study was performed through spectrophotometric assay, with p-nitrophenyl-α-d-glucopyranoside as a substrate with varying concentrations. An in vitro antioxidant study was performed by DPPH assay. In addition, UPLC-QTOF-MS analysis was carried out for metabolite profiling of the bioactive fraction of C. grandis. The results showed that the difference between the α-glucosidase inhibitory activity of the ethyl acetate fraction of C. grandis (EFCG) (IC50 2.43 ± 0.27 mg/ml), and standard inhibitor, acarbose (2.08 ± 0.19 mg/ml), was not statistically significant at a P-value of 0.05. The enzyme kinetics confirmed the inhibition mode in a mixed manner. The EFCG also showed the highest antioxidant activity (101.74 ± 1.95 µg/ml) among all of the fractions. A significant correlation between antioxidant and α-glucosidase inhibitory activity of EFCG was observed. The LC-QTOF-MS study of the EFCG putatively identified 35 metabolites, which may be responsible for its antioxidant and α-glucosidase inhibitory properties. Thus, C. grandis fruits can serve as a functional food to address diabetes-related disorders associated with α-glucosidase.