Triterpene isolated from Rosa sp.

Secondary metabolites, also known as natural products, are present in plants and have tremendous potential to the discovery of new pharmaceuticals, neutraceuticals, and agrochemicals. Alimboyoguen and Ragasa (CaVSU) investigated the secondary metabolite chemistry of Rosa sp., commonly known as the red rose, which is known to have a wide range of medicinal applications. The study aimed to isolate the secondary metabolite from the dichloromethane (DCM) extracts of the flowers of Rosa sp. using chromatographic methods, elucidate the structure of the isolate by the application of infrared, 1-dimensional and 2-dimensional nuclear magnetic resonance (NMR) spectroscopy, and determine the antimicrobial activity of the isolated compound. Air-dried flowers of Rosa sp. were ground in an osterizer, soaked in dichloromethane for 3 days and filtered. The filtrate was concentrated under vacuum to obtain crude extract. This was purified using silica gel chromatography with increasing proportion of acetone in DCM at 10% increment as diluting solvent. The 60% acetone in DCM fraction was rechromatographed and fractions 3-5 were combined and again rechromatographed. Fractions 2-3 were obtained and washed with diethyl ether. The pure isolates were subjected to spectroscopic analyses using infrared (IR) and extensive NMR spectroscopic techniques for structure elucidation. The NMR spectroscopic analyses were performed at the Central Queensland University, Australia. Antimicrobial activity tests were conducted by the Natural Science Institute (NSRI) at UP Diliman [Quezon City, Philippines]. The agar cup well method was used on the following test organisms: 2 gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis); 2 gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli) and 3 fungi (Candida albicans, Trichophyton mentagrophytes, and Aspergillus niger). Findings of the study revealed the following: A triterpene was isolated from the flowers of Rosa sp. The compound was colorless solid, with Rf value sp. of 0.44. It produced in thin layer chromatography (TLC) characteristic dark blue violet spot when visualized with vanillin-sulfuric acid. Based on the extensive one-dimensional (1D) and two-dimentional (2D) NMR analyses, the compound from the DCM extract was identified as 2-oxopomolic acid. Although 2-oxopomolic acid is relatively common this was the first report on the complete NMR assignments of the compound, using 1D and 2D analyses. The structure of 2-oxpomolic acid was similar with pomolic acid, a well-known anti-HIV and anti-cancer agent. Antimicrobial tests indicated that at a concentration of 30 ug, this compound was active against the fungi, Candila albicans and Trichophyton mentagrophytes; slightly active against the bacteria, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus; and inactive against Bacillus subtilis and Aspergillus niger. Further study on the isolation and structure elucidation of other constituents and their biological activities, and conduct of anti-HIV and anti-cancer tests to determine their potential against these diseases are recommended.