Characterization of Volatile Compounds and Biological Effects Capacities of Moroccan Thymus capitatus L., Essential Oils: In Vitro and In Silico Approaches

Abstract

The present study investigated the phytochemical composition of Thymus capitatus L. essential oil (TCEO) harvested in Morocco using GC–MS–MS analysis. Both in vitro and in silico approaches were combined to investigate the antioxidant, antibacterial, antidiabetic, dermatoprotective, and neuroprotective properties of TCEO as well as to identify the main compounds responsible of the promising properties. The TCEO was dominated by oxygenated monoterpene (63.33%) and monoterpene hydrocarbon (23.25%). In total, 20 volatile compounds were identified, and of them, carvacrol, thymol, p-cymene, γ-terpinene, caryophyllene, and linalool are the major compounds. Then, the study of the antioxidant activity revealed that TCEO exhibits a good activity in DPPH, ABTS, and FRAP assays as the obtained values were 67.34 ± 1.54, 96.88 ± 2.76, and 99.07 ± 1.57 µg/mL, respectively, compared to those of Trolox (35.38 ± 0.91, 60.40 ± 1.55, and 52.13 ± 1.56 µg/mL, respectively). The antibacterial activity revealed that TCEO was the most active toward the two Gram-positive bacteria (Staphylococcus aureus and Listeria monocytogenes) with minimum inhibitory concentration (MIC) of 0.125% each compared to Gram-negative ones (Pseudomonas aeruginosa and Escherichia coli) with MIC of 0.25% and 0.5%, respectively. For the antidiabetic tests, TCEO displayed markedly lower IC₅₀ values, 111.79 ± 2.88 µg/mL for α-amylase and 70.42 ± 1.68 µg/mL for α-glucosidase than those of acarbose (389.04 ± 1.65 and 187.82 ± 2.62 µg/mL, respectively). For anti-elastase activity, TCEO exhibited an IC₅₀ value of 42.58 ± 1.72 µg/mL, indicating moderate inhibitory potency, whereas quercetin demonstrated a significantly stronger effect with an IC₅₀ of 11.81 ± 0.90 µg/mL. In terms of anti-tyrosinase activity, TCEO showed an IC₅₀ of 85.55 ± 2.51 µg/mL, which is notably more effective than quercetin's IC₅₀ of 242.99 ± 2.67 µg/mL. The study of neuroprotection ability revealed that TCEO exerted a good effect as the inhibition of acetylcholinesterase (AChE) was 12.36 ± 0.93 mg GALAE/g, whereas that of butyrylcholinesterase (BChE) was 3.59 ± 0.64 mg GALAE/g. On the basis of these findings, it is believed that TCEO can serve as a readily available reservoir of natural antioxidants and antibacterial chemicals. TCEO could also provide considerable benefits for health, including antidiabetic, dermatoprotection, and neuroprotection capacities.