Chemical composition and cholinesterase, tyrosinase, alpha-amylase and alpha-glucosidase inhibitory activity of the essential oil of Salvia tomentosa

Abstract

The aim of this study was to determine the chemical composition of Salvia tomentosa (Miller) essential oil and to examine its inhibitory effect on acetylcholinesterase (AChE), butyrylcholinesterase (BChE), tyrosinase, α-amylase and α-glucosidase in vitro. In this study, the interaction between the main components of essential oil and the enzymes in question was analyzed through molecular docking analyses. The presence of 60 compounds representing 98.2% of the essential oil was determined. The major compounds of the oil were camphor (9.35%), γ-muurolene (8.37%), α-pinene (7.59%), α-caryophyllene (6.25%), viridiflorol (5.13), δ-cadinene (5.01%), and terpinene-4-ol (5.01 %). The oil exhibited higher inhibitory activity on BChE than on AChE. The BChE inhibitory activity of the oil was determined to be 16.48 mg GALAEs/g. The oil showed 47.13 mg KAEs/g inhibitory activity on tyrosinase. The inhibitory activities of the essential oil on α-glucosidase and α-amylase were determined as 703.29 and 694.75 mg ACEs/g, respectively. Based on docking binding energies, δ-cadinene, viridiflorol, γ-muurolene and α-caryophyllene were determined to be the most promising ligands showing the highest affinity (min. -6.90 kcal/mol; max. -8.40 kcal/mol) against α-amylase, AChE and BChE. However, all four ligands were found to exhibit low affinity (min. -5.50 kcal/mol; max. -5.90 kcal/mol) against tyrosinase. Considering in silico physicochemical properties, drug-like features (Lipinski's rule of 5) and intracellular targets, δ-cadinene, viridiflorol, γ-muurolene and α-caryophyllene possess hit features and do not show non-specific enzyme or protein affinity. Ligand binding assays (LBA) to be performed between the monoterpenes and enzymes in question may constitute the next step in confirming their competitive inhibitory capacity.