ISOLATION AND FUNCTIONAL GROUP TRANSFORMATION OF XANTHONE FROM PERICARP GARCIANA MANGOSTANA AND THEIR ANTI-BACTERIAL ACTIVITY

• Main Author: Ulfah, Mariam
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/38323
• Institution: Institut Teknologi Bandung

Garcinia mangostana (Guttiferae) is a tropical tree extensively distributed in Southeast Asia. This species has various uses in traditional medicine, such as for treatment of tuberculosis, skin infection, diarrhea and inflammation. The phytochemical studies showed that G. mangostana is a source of xanthone- derivatives, especially prenylated xanthone. ?-Mangostin (1) is a major prenylated xanthone isolated from G. mangostana, which were found to have anti-oxidant, anti-inflammatory, cytotoxic, and anti-fungal activities. However, studies of anti- bacterial activities of this compound are limited. The growing number of anti- microba resistance anti-biotic encourages researchers to observe for anti-bacterial agent, one example with chemical transformation. ?-Mangostin (1) contains functional group such as hydroxyl and prenyl group which potential to be transformed through several types of reaction such as reduction, oxidation, substitution and ring-closing metathesis (RCM) reaction. Semisynthetic compounds derived from ?-mangostin (1) also has been previously reported for its high bioactivity properties. However, the RCM reaction carried out on ?- mangostin (1) has never been reported. Therefore, this research reports an isolation of xanthones from pericarp G. mangostana and a formation of oxepin ring in ?-mangostin (1) through allylation and RCM reaction. In addition, anti- bacterial activity of ?-mangostin (1) and derivatives also carried out against ten bacteria (six Gram-(+) bacteria and four Gram-(-) bacteria). Isolation of the xanthone compounds carried out through extraction (maceration) of pericarp G. mangostana, fractionation, and purification. Fractionation and purification were done using various chromatographic techniques, such as vacuum, column and radial chromatography. Semisynthesis of ?-mangostin (1) derivatives was carried out using allylation method. Furthemore, RCM reaction performed to allylation reaction product. Structure of the molecules of both isolated and semisynthetic compound were determined based on spectroscopic data, including 1D NMR (1H- NMR, 13C-NMR) and 2D-NMR (COSY, HMBC, HSQC) and MS. In this research, four compounds have successfully isolated and characterized as: ?- mangostin (1), 9-hydroxycalabaxanthone (2), 2-(?,?-dimethylalyl)-1,7-dihydroxy- 3-methoxyxanthone (3) and tovofilin A (4). Allylation reaction yielded 6-O-allyl- ?-mangostin (5) and 3,6-di-O-allyl-?-mangostin (6). Furthermore, RCM reaction performed to 3,6-di-O-alyl-?-mangostin (6) gave 6-alyloxy-1-hydroxy-7- methoxy-8-prenyl-2',5'-dihydro-2,3-oxepinoxanthone (7) and 6-alyloxy-1- hydroxy-7-methoxy-8-prenyl-2'-dihydro-2,3-oxepinoxanthone-3'-on (8). Compounds 7 and 8 were new synthetic analogues of 1. Antibacterial activities of compound 1-8 was evaluated against ten bacteria, showing that 1 was the most active with the zone of inhibition were in the range of 7-15 mm. This result indicated that either the hydroxyl group at C-6 and/or in combination with the prenyl groups at C-2 and C-8 in ?-mangostin (1) are essential for antibacterial properties of xanthones.