Chemical constituents and bioactivity of Malaysian and Indonesian kaempferia rotunda

Abstract

The essential oils and the phytochemicals of the rhizomes of Kaempferia rotunda cultivated in Malaysia and Indonesia have been studied. Hydrodistillation of the fresh rhizomes of K. rotunda gave 0.09% and 0.23% oils respectively. These oils were analyzed by GC (Kovats Indices) and GC-MS. The main constituents found in the rhizome oil of Malaysia were bornyl acetate (9.6%), benzyl benzoate (8.4%) and camphor (5.6%), while the rhizome oil from Indonesia was rich in benzyl benzoate (87.7%) and n-pentadecane (4.2%). Extractions by soxhlet apparatus were carried out on the dried samples to get the crude extracts. Fractionation and purification on the crude extracts resulted in the isolation of three new cyclohexane oxides and ten known compounds, comprising of cyclohexane oxides, esters, carboxylic acid, labdane diterpene, and flavonoids. Two new compounds identified as 2- (benzoyloxymethyl)phenyl (3-O-acetyl)-ß-glucopyranoside and 3-debenzoylrotepoxide A, together with seven known compounds, crotepoxide, 4- benzoyloxymethyl-3,8-dioxatricyclo[5.1.0.02,4]octane-5,6-diol 5-acetate, 1,6- desoxypipoxide, curcumrinol C, 2'-hydroxy-4,4',6'-trimethoxychalcone and naringenin 4',7-dimethyl ether were isolated from the Malaysian species, while a new compound identified as 3-acetoxy-2-benzoyloxy-1-(benzoyloxymethyl)-cyclohexa- 4,6-diene with the seven known compounds namely crotepoxide, 4- benzoyloxymethyl-3,8-dioxatricyclo[5.1.0.02,4]octane-5,6-diol 5-acetate, 1,6- desoxypipoxide, 6-acetylzeylenol, trans-docosyl ferulate, benzyl benzoate and benzoic acid were isolated from the Indonesian species. The structures of all compounds were established based on spectral studies using MS, IR, UV and NMR spectroscopies. Naringenin 4',7-dimethyl ether, curcumrinol C, trans-docosyl ferulate, and benzoic acid were found for the first time from K. rotunda and also the genus of Kaempferia. Antibacterial and antioxidant screening assays using discdiffusion method and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) method, respectively were carried out on the crude extracts and essential oils. The crude extracts and essential oils of K. rotunda from Malaysia and Indonesia did not show activities on antibacterial and antioxidant assay.