Morphology, Anatomy and Secondary Metabolites Investigations of Premna odorata Blanco and Evaluation of Its Anti-Tuberculosis Activity Using In Vitro and In Silico Studies

Abstract

In-depth botanical characterization was performed on Premna odorata Blanco (Lamiaceae) different organs for the first time. The leaves are opposite, hairy and green in color. Flowers possess fragrant aromatic odors and exist in inflorescences of 4-15 cm long corymbose cyme-type. In-depth morphological and anatomical characterization revealed the great resemblance to plants of the genus Premna and of the family Lamiaceae, such as the presence of glandular peltate trichomes and diacytic stomata. Additionally, most examined organs are characterized by non-glandular multicellular covering trichomes, acicular, and rhombic calcium oxalate crystals. P. odorata leaves n-hexane fraction revealed substantial anti-tuberculous potential versus Mycobacterium tuberculosis, showing a minimum inhibition concentration (MIC) of 100 μg/mL. Metabolic profiling of the n-hexane fraction using gas-chromatography coupled to mass spectrometry (GC/MS) analysis revealed 10 major compounds accounting for 93.01%, with trans-phytol constituting the major compound (24.06%). The virtual screening revealed that trans-phytol highly inhibited MTB C171Q receptor as M. tuberculosis KasA (β-ketoacyl synthases) with a high fitting score (∆G = -15.57 kcal/mol) approaching that of isoniazid and exceeding that of thiolactomycin, the co-crystallized ligand. Absorption, distribution, metabolism, excretion and toxicity predictions (ADME/TOPKAT) revealed that trans-phytol shows lower solubility and absorption levels when compared to thiolactomycin and isoniazid. Still, it is safer, causing no mutagenic or carcinogenic effects with higher lethal dose, which causes the death of 50% (LD50). Thus, it can be concluded that P. odorata can act as a source of lead entities to treat tuberculosis.