Abstract
The main objective of cancer treatment with chemotherapy is to kill the cancerous cells without affecting the healthy normal cells. In the present study, bioactivity-guided purification of the n-chloroform soluble fraction from the methanol extract of Roscoea purpurea resulted in the identification of two new labdane diterpenes: coronarin K (1) and coronarin L (2), along with eight known compounds, coronarin A (3), bisdemethoxycurcumin (4), kaempferol 3-O-methyl ether (5), kaempferol (6), fenozan acid (7), 3-(3-methoxy,4-hydroxyphenyl)-2-propenoic acid ferulic acid (8), caffeic acid (9), and gallic acid (10). The structural identification of new compounds (1 and 2) were determined by detailed analysis of 1D (1H and 13C) and 2D NMR (COSY, HSQC, and HMBC) spectroscopic data. The relative configurations of 1 and 2 were determined with the help of NOESY correlations and comparison of optical rotations with known labdane diterpenes, with established stereochemistry, while structure of known compounds was established by direct comparison of their NMR data with those reported in the literature. This is the first report of isolation of this labdane diterpenes and phenolic classes of secondary metabolites in R. purpurea. In the preliminary screening, the methanol extract and its fractions were tested for the cytotoxic activity against a panel of four cancer cell lines (A549, HCT-116, Bxpc-3, and MCF-7); extract and its chloroform fraction were found to be active against the lung cancer cell line, A-549, with IC50 value <25 μg/ml. Owing to the notable cytotoxic activity of the chloroform fraction, the compounds (1–5) were screened for their cytotoxicity against all the cell lines by MTT assay. Coronarin K, 1 showed significant cytotoxic potential against lung cancer cell lines (A-549), with IC50 value of 13.49 μM, while other compounds did not show activity below 22 μM.
Highlights
In our continuing research program to discover bioactive natural products from natural resources, especially from high-altitude Himalayan endangered medicinal plants, with profound biological activities, our attention was focused on the rhizomes of Roscoea purpurea, commonly known as kakoli, which belongs to the family of Zingiberaceae that is abundantly available in alpine grassland, Novel Diterpenes From Roscoea purpurea grassy hillsides, and stony slopes of central to eastern Himalaya from Uttarakhand to North East states, up to an altitude of 3,300 m
By the cytotoxic activity-guided isolation of R. purpurea extract, we have made an unusual finding of two new labdane diterpenes coronarin K (1) and coronarin L (2), together with the other known compounds 3–10
We have evaluated the anti-cancer activity of extract, chloroform fraction, and isolated compounds
Summary
In our continuing research program to discover bioactive natural products from natural resources, especially from high-altitude Himalayan endangered medicinal plants, with profound biological activities, our attention was focused on the rhizomes of Roscoea purpurea, commonly known as kakoli, which belongs to the family of Zingiberaceae that is abundantly available in alpine grassland, Novel Diterpenes From Roscoea purpurea grassy hillsides, and stony slopes of central to eastern Himalaya from Uttarakhand to North East states, up to an altitude of 3,300 m It is an essential ingredient of an important Ayurvedic preparation, known as Astavarga, which is a group of eight plants claimed to be useful for healing weakness, body overweight, bone fractures, high fever, and diabetic situations, as well as for healing vata, pitta, and rakta doshas (Dhyani et al, 2010). We have described isolation and structure elucidation of two new compounds from the rhizomes of R. purpurea and the anti-cancer activities of plant extract, fractions, and isolated compounds
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