ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Enzymatic glycosylation of menthol: optimization of synthesis and extraction processes using response surface methodology and biological evaluation of synthesized product

Shafaq Nisar, Muhammad Asif Hanif, Muhammad Zahid, and Abdul Ghaffar

Department of Chemistry, University of Agriculture, Faisalabad, Pakistan

E-mail: drmuhammadasifhanif@gmail.com

Received: 31 August 2021  Accepted: 31 December 2021

Abstract:

Menthol, due to inherent refreshing feeling and mint flavour, has been extensively used in food, pharmaceutical, flavor and fragrance products. However, menthol has low solubility in water. That is why, the applications of menthol have been confined and a menthol substance with good water solubility is much desired. Hence, glycoside compounds are an excellent choice, which have very low vapour pressures, are water soluble and highly stable. These derivatives can be prepared using biocatalytic method and release only a nontoxic anchor-molecule. In this research, glycosylation process was carried out to synthesize menthyl glucoside (MenG) enzymatically as it has been found that glycoside compounds have good water solubility and can be stored easily due to non-volatility. The menthyl glucoside was synthesized by the reaction of maltose with menthol in the presence of alpha glucosidase enzyme. Various factors affecting the synthesis (amount of menthol and maltose, temperature, enzyme concentration and time) and extraction (reaction mixture to solvent ratio, number of cycles and extraction time) of MenG were optimized using RSM. Maximum obtained yield of MenG under optimized synthesis reaction conditions (amount of menthol and maltose of 1 g and 3 g, respectively, temperature of 45℃, time of 20 h and enzyme concentration of 200U) and extraction conditions (reaction mixture to solvent ratio of 1:3 number of cycles of 3 and extraction time of 1.5 h) was 49.7 ± 0.2%. Separation and purification of synthesized products were done using chromatographic techniques. Furthermore, observed biological activities (antioxidant, antibacterial, antifungal and insecticidal activities) of the MenG were found to be comparable with that of menthol.

Keywords: Menthol; Glycosylation; Glycosides; Response surface methodology; Menthyl glucoside

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-022-02061-y

Chemical Papers 76 (5) 2649–2675 (2022)