Phenolic compounds from Serenoa repens fruit

Abstract

Fruit of Serenoa repens (W. Bartram) Small (saw palmetto) (Arecaceae) is used in folk and scientific medicine to treat and prevent prostate hyperplasia and non-bacterial prostatitis [1]. Information about the chemical composition of the fruit is limited to data on the lipid complex and the presence in them of flavonoids, despite broad pharmacological studies of S. repens preparations [2]. The goal of the present work was to study the composition of phenolic compounds from S. repens fruit. Fruit of S. repens was supplied by Pacific Botanicals (USA). The species was determined by Cand. Pharm. Sci. G. B. Chekhirova (IGEB, SB, RAS, Ulan-Ude). A sample of the raw material was preserved in the herbarium of IGEB, SB, RAS (No. Asm-37/25-98/0912). Extraction and Fractionation. Fruit of S. repens (400 g) was separated beforehand into pericarp and seeds, the ratio of which was 1.34:1, in order to fractionate the extracted substances. Then, raw material was ground and defatted in a Soxhlet apparatus using hexane. The remaining raw material was dried and extracted with EtOH (96, 70, and 50%; 5 ; 90°C). The EtOH extracts were combined and concentrated in vacuo to an aqueous residue that was subjected to liquid–liquid extraction by CHCl3, EtOAc, and BuOH. This produced fractions of pericarp (FP) and seeds (FS) from CHCl3, FP-1 (0.25% yield of airdried raw material mass) and FS-1 (0.13%); EtOAc, FP-2 (0.43%) and FS-2 (0.18%); BuOH, FP-3 (1.99%) and FS-3 (0.73%); and H2O, FP-4 (9.79%) and FS-4 (2.45%). Fraction FP-1 (520 mg) was separated by column chromatography (CC) over polyamide (2 40 cm, eluent H2O:EtOH, 100:0 4:96) and Sephadex LH-20 (2.5 90 cm, eluent CHCl3:Me2CO, 100:0 70:30) to afford six compounds. These were protocatechoic (4 mg, 1), 4-hydroxybenzoic (2 mg, 2), pyrocatechoic (11 mg, 3), syringic (2 mg, 4), veratric (9 mg, 5) [3], and o-coumaric acids (4 mg, 6) [4]. Separation of fraction FS-1 (220 mg) under analogous conditions produced three compounds. These were 1 (4 mg), 2 (12 mg), and isovanillic acid (9 mg, 7) [3]. The minor components of the fractions were determined by GC-MS as TMS-derivatives (Table 1). As a result, 19 compounds were found in FP-1. These were 1–6; 3-hydroxybenzoic (7); 3-methoxybenzoic (m-anisic, 8); 4-methoxybenzoic (p-anisic, 9); 2,4-dihydroxybenzoic (10); 2,5-dihydroxybenzoic (gentisic, 11); 2,6-dihydroxybenzoic (12); 3,5-dihydroxybenzoic (13); 2-hydroxy-3-methoxybenzoic (14); 3-hydroxy4-methoxybenzoic (isovanillic, 15); 2-hydroxy-5-methoxybenzoic (16); 3-methoxy-4-hydroxybenzoic (vanillic, 17); p-coumaric (18); and ferulic acids (19). Fraction FS-1 yielded 10 compounds (1-5, 7, 11, 12, 15, 17). Distinguishing features of the seed fraction (FS-1) were the lack of phenylpropanoids, the content of which in the pericarp fraction (FP-1) was 2.50%, and the higher content of monohydroxy-substituted benzoic acids (6.86%) and lower content of methoxylated acids. The contents of the dominant components in the fractions (%) were 3 (3.96), 5 (3.27), and 6 (1.37) in FP-1 and 1 (2.74), 2 (6.46), and 15 (5.57) in FS-1.