Chemical and Biological Study of Flueggea virosa Native to Saudi Arabia

Abstract

Flueggea virosa (Roxb. ex Willd.) Royle (Phyllanthaceae), also known as Chinese waterberry, is a shrub up to 4 m high growing wild in tropical Africa, Middle East, tropical Asia, Japan, Australia, and Polynesia and can also be grown domestically. It has many recorded uses in Chinese herbal medicine. The plant has been used for the treatment of fever, malaria, sexual dysfunction, pain, diabetes, epilepsy, snakebite, venereal disease, rheumatism, arrhythmia, rash, diarrhea, pneumonia, cough, hepatitis, and HIV-related illness, and as a contraceptive [1, 2]. The methanol and water extracts of the plant have been reported to possess a number of biological activities such as antiplasmodial, trypanocidal, and antiarrhythmic [3, 4]. Previous phytochemical studies of F. virosa showed the presence of triterpenoids [2], tannins, flavonoids, saponins [5, 7], resins, glycosides, glycerin carbohydrates, anthraquines, steroids [5], alkaloids [6, 8], cardiac glycosides [5, 6], and anthraquinones [6]. In our phytochemical investigation of this plant [9], a total of 14 compounds were isolated from the ethanolic extract of the aerial parts of F. virosa, collected from the Southern part of Saudi Arabia, in June 2000. The plant (air-dried crushed aerial parts, 1 kg) was macerated with 95% EtOH at room temperature overnight (1 L each 3). The dried crude EtOH extract (40 g) was dissolved in 0.1 N HCl (1 L; pH 1) and partitioned with n-hexane and n-BuOH (500 mL 3) successively. The n-BuOH fraction was subjected to flash column chromatography (CC) over silica gel to afford bergenin [white crystals, mp 236–238 C (1, 10 g)], menisdaurin [brown solid, mp 172–173 C (2, 1 g)] and amiroside [brown solid, mp 176–178 C (3, 25 mg)] [9, 10]. The defatted aqueous acidic fraction was basified with NH4OH (pH 11) and partitioned with EtOAc. The EtOAc fraction (3 g) was subjected to flash chromatography on silica gel with further purification using reverse phase CC over C-18 silica gel (MeCN–H2O, 9:1) to afford ent-phyllanthidine [yellow white crystals, mp 158–160 C (4, 30 mg)] [11], securinine [white powder, mp 140–142 C (5, 8 mg)], securinol [white powder, mp 136–137 C (6, 6 mg)], viroallosecurinine [dark yellow solid, mp 130–132 C (7, 40 mg)] [12], flavonoid rutin [yellow solid, mp 194–195 C (8, 40 mg)] [13], gallocatechin (9) and epi-gallocatechin [white solid, mp 188–190 C] (10, mixture, 12 mg) [14], 2,2 ,5,5 -tetrahydroxybiphenyl [white solid, mp 144–145 C (11, 12 mg)], ethylmanopyranoside [white solid, mp 154–156 C (12, 132 mg)], ethyl glucopyranoside [white powder, mp 163–164 C (13, 9 mg)] [9], and the triterpene precursor squalene [oil (14, 20 mg)] [15]. The identity of all the isolated compounds was confirmed by direct comparison with authentic samples, as well as their physical and spectral data (UV, IR, NMR and MS) with those published in the literature. This is the first report of the cyanogenetic glucosides menisdaurin (2) and amiroside (3) isolated from the genus Flueggea, as well as from the plant family Phyllanthaceae. They were previously reported from Ilex aquifolium and Guazuma ulmifolia [16].