Chemical Composition and Bioactivity of Essential Oil of Seed and Leaf from Alpinia speciosa Grown in Taiwan

Abstract The essential oil, methanolic and aqueous extracts of the seeds and leaves of Alpinia speciosa (Wendl.) K. Schum. (Zingiberaceae) were assayed for their mushroom tyrosinase inhibition, larvicidal effect, antioxidant property and antimicrobial activity. The main components of the seeds were camphor, sabinene, (Z)‐β‐ocimene, 1,8‐cineole, terpinen‐4‐ol and α‐pinene, while the leaves contains camphor, sabinene, γ‐terpinene, terpinen‐4‐ol and α‐terpineol. The seed and leaf oil exhibited concentration‐dependent inhibition of mushroom tyrosinase, giving 74 and 81% inhibition at 1000 ppm, respectively. The seed oil exhibits the mosquito larvicidal activity with 2 h and 24 h LC 50 value of 125 and 87 ppm, respectively, whereas the leaf oil shows larvicidal activity with 2 h and 24 h LC 50 value of 64 and 32 ppm, respectively. The methanolic and aqueous extracts of A. speciosa show remarkable antioxidant effect. This activity can be attributed to the presence of the phenolic compounds. The essential oil of A. speciosa exhibits a strong broad‐spectrum antimicrobial activity against all test organisms. The seeds and leaves of A. speciosa could be considered as a natural tyrosinase inhibition, mosquito larvicidal, antioxidant and antimicrobial source.