A Comprehensive Review of Traditional Uses, Phytochemistry, Pharmacological Activities, Toxicity and Research Priorities of Leucas Aspera (Thumbai)

Abstract

Leucas aspera (Willd.) Link, belonging to the family Lamiaceae, is a widely distributed annual herb commonly known as “Thumbai” or “Thumba” in India and other parts of South and Southeast Asia. The plant has a long history of traditional medicinal use for the treatment of fever, cough, cold, asthma, respiratory disorders, inflammation, wounds, skin diseases and insect bites. Leaves, flowers and aerial parts are commonly used in traditional medicine because of their diverse therapeutic properties. Phytochemical studies have revealed the presence of several important secondary metabolites, including triterpenoids, steroids, diterpenes, flavonoids, phenolic compounds, alkaloids, tannins and essential oils. Important constituents reported from the plant include oleanolic acid, unsolid acid and β-sitosterol. Characteristic compounds such as leucasperones and leucasperols have also been identified, indicating significant chemical diversity. These constituents may contribute to the pharmacological properties of the plant. Preclinical investigations using in-vitro, in-vivo and in-silico models have demonstrated several pharmacological activities, including antioxidant, anti-inflammatory, antimicrobial, antifungal, anticancer, cytotoxic, antinociceptive, antipyretic, hepatoprotective, antivenom and insecticidal effects. The antioxidant activity is mainly associated with phenolic and flavonoid compounds that can scavenge free radicals and reduce oxidative stress. Antimicrobial studies have also demonstrated inhibitory effects against various pathogenic microorganisms, supporting some of its traditional applications. Toxicological studies generally indicate relatively low toxicity at commonly investigated experimental doses; however, comprehensive human clinical evidence remains limited. Further research is therefore required to standardize extracts, identify active phytoconstituents, clarify molecular mechanisms, assess long-term toxicity and conduct well-designed clinical trials. Overall, L. aspera represents a promising medicinal plant with considerable phytochemical diversity and broad pharmacological potential.