Chemical composition, antifungal activity and molecular docking of Himalayan thyme leaf extract (Thymus linearis) against fish pathogenic oomycete Saprolegnia parasitica

Abstract

The present investigation estimated the potential anti-oomycetes activity of Thymus linearis leaf extract and identified the phytochemical compounds by Gas chromatography-Mass spectrometry (GC-MS). Saprolegnia parasitica isolated from the golden mahseer, Tor putitora was used for efficacy study. The effect of T. linearis plant extract on hyphal growth, zoospore production was employed by a agar diffusion method and microwell plate, respectively. The ethanolic extract of T. linearis exhibited hyphal growth inhibition to 54.45 ± 0.9% at 0.32 mg ml−1 and complete inhibition (100%) at 5.12 mg ml−1. The zoospore production was ultimately arrested at 0.32 mg ml−1 against S. parasitica. A total of 18 volatile constituents were identified from the GC–MS of the whole plant extract. The major volatile constituents in the extracts were ethyl (9z, 12z)-9, 12-octadecadienoate (22.58%), palmitic acid (11.95%), ethyl palmitate (9.89%), phytol (5.03%), stigmast-5-En-3-Ol, (3.Beta.)- (4.54%), (Z, Z)-6, 9-Cis-3, 4-epoxy-nonadecadiene (3.60%), carvacrol (3.59%), cryptomeridiol (3.22%), Heptadecanoic acid, ethyl ester (2.03%) and naphthalene, decahydro-(1.28%). Molecular docking was performed by Auto Dock Vina 4.0 of the constituents for obtaining the binding mode predictions with target proteins of S. parasitica. Phytol and carvacrol were identified to interact with plasma membrane ATPase, host target protein-1 and TKL protein kinase and V-type protein ATPase. Molecular interaction of phytol was stronger to V-type protein ATPase. From the results, it is evident that T. linearis contain various natural compounds and is recommended plant of phytopharmaceutical importance. T. linearis extract could be explored as antioomycetes compounds for treating oomycetes infections, saprolegniasis in aquaculture.