In vitro and in silico pharmacological effects of Rosmarinus officinalis leaf methanolic extracts and essential oils

Rosmarinus officinalis L. has been widely used as a spice to enhance the shelf-life of food for centuries. While existing research in the literature suggests that the primary antibacterial component of this plant is its essential oil (EO), there is a lack of comparative studies employing both in vitro and in silico approaches to evaluate the antimicrobial, antioxidant, anticancer, and antidiabetic properties of R. officinalis leaf EO (ROLEO) and R. officinalis leaf methanolic extract (ROLME). The present study investigates the bioactive components and biological activities of ROLEO and ROLME using gas chromatography-mass spectrometry analysis. Additionally, the total phenolic content (TPC) and total flavonoid content (TFC) were quantified, and their antioxidant, antidiabetic, anticancer, and antibacterial activities were evaluated in vitro and in silico studies. GC-MS analysis revealed 20 bioactive compounds of ROLME, compared to 73 bioactive compounds in ROLEO. The TPC of ROLEO was higher, measuring 49.34 ± 2.84 mg GAE per gram of dry weight of the extract, compared to ROLME, which had a TPC of 38.13 ± 3.31 mg GAE per gram of dry weight of the extract. The TFC of ROLEO was measured at 24 ± 1.47 mg QE/g of dry weight, which is higher than that of ROLME, measured at 19 ± 1.47 mg QE/g of dry weight. Additionally, ROLEO demonstrated superior antioxidant activity at low concentrations compared to ROLME and greater antidiabetic properties by suppressing the actions of α-amylase and α-glucosidase enzymes. Moreover, ROLEO showed promising anticancer effects at lower doses, and antibacterial capabilities, particularly against Gram-positive bacteria. Molecular docking studies have identified key components of ROLEO that exhibit significant bioactivity. Among these compounds, 1H-Cycloprop[e]azulen-4-ol, decahydro-1,1,4,7-tetramethyl-, [1ar-(1α,4β,4aβ,7α,7aβ,7bα)]-demonstrated the highest activity against α-amylase, while thymol exhibited the strongest activity against caspase-3 and E. coli gyrase B. Overall, molecular docking and pharmacokinetic analysis identified promising inhibitory effects of key ROLEO compounds on α-amylase, caspase-3, and E. coli gyrase B, with favorable drug-like properties. These findings suggest that the EO of R. officinalis may serve as the basis for the development of innovative synthetic medications, offering valuable insights for the pharmaceutical industry to design novel treatments for various diseases.