CONICET | Buscador de Institutos y Recursos Humanos

Recently, we have reported that some extracts, obtained from aerial parts of Heterophyllaea lycioides (Rusby) Sandwith (Rubiaceae), showed in vitro antibacterial activity against Gram-positive and Gram-negative bacteria. This plant belongs to a genus characterized by the presence of anthraquinones (AQs). With the aim to find a relationship between antibacterial activity and chemical composition, a HPLC method was developed for identification and quantification of AQs in the extracts. The four extracts previously tested for antibacterial activity, hexane (Hx), benzene (Ben), ethyl acetate (AcOEt) and ethanol (EtOH), were analyzed by HPLC. A C18 column was used, with a gradient program of two mobile phases: a) MiliQ water and b) methanol (MeOH) (both with 0,612 % V/V of formic acid) at 0.4 mL/min, and detection at 269 nm. Identification of AQs was performed by comparison of the retention time with the corresponding standard (AQs purified and unequivocally identified by their spectroscopic data). The percentage of each AQ in dried extract was expressed as Soranjidiol (Sor) by means of the external calibration method. HPLC analysis revealed the presence of Sor, Bisoranjidiol (Bis), Pustuline (Pus), Heterophylline (Het), Chloro-soranjidiol (Cl-sor), 2-OH-3-methyl-anthraquinone (2-OH-3-Me-AQ), and two AQs that are in elucidation process (AQ-1 and AQ-2). Thus, several known AQs that had not been isolated yet from this vegetal species were identified. Sor, Bis and Pus are the most important AQs because they were detected in all extracts, in spite of AQ-1 was the most abundant compound but it was only found in AcOEt and EtOH. Het, Cl-sor, 2-OH-3-Me-AQ and AQ-2 were present in small amounts and only in some extracts. Since the bioactive extracts, AcOEt and Ben, possess a wide variety of AQs in high amount, we would conclude that exist a strong relationship between the antibacterial activity and the composition of AQs in the extracts.