Is Hyptis lacustris A. St.-Hil. ex Benth. (Lamiaceae) extract a good candidate for antibacterial uses?

Abstract

More than 70% of drugs approved during the last three decades to treat bacterial infection are derived from natural products. Lamiaceae is one of the ten most researched families regarding its medicinal uses. Hyptis Jacq. (Lamiaceae) is used in popular medicine of several countries, including northeast part of Brazil, for the treatment of gastrointestinal infections, cramps, pains, skin diseases, malaria, respiratory diseases, and insect repellent. Hyptis lacustris A. St.-Hil. ex Benth. is used by Yanesha tribe of Peru for the treatment of cutaneous leishmaniasis. In vitro studies confirmed its ethnopharmacological use, in which 95% ethanol extract showed Inhibitory Concentration of 50% lower than 10 μg mL−1 against axenic amastigotes of Leishmania amazonensis. For its use in traditional medicine, the aim of this research was to investigate the antibacterial activity of hydroethanol crude extract and its four fractions (hexane, dichloromethane, ethyl acetate, and hydromethanol) against three bacteria strains (Bacillus subtilis, Pseudomonas aeruginosa, and Escherichia coli), and the activity of three compounds isolated from Hyptis lacustris against Bacillus subtilis. The extract was produced by maceration of stems and leaves in 70% ethanol, and its fractions were produced by partition using hexane, dichloromethane, and ethyl acetate. Fractions were chemically characterized using gas chromatography coupled with mass spectrometry and high-performance liquid chromatography coupled with a diode array detector. Compounds from fractions with high antibacterial activity were purified and identified through Nuclear Magnetic Resonance and Mass Spectrometry. The antibacterial activity of extract, fractions, and isolated compounds were screened by a broth microdilution method in 96-wells microplate. Major constituents in the hexane fraction are terpenoids, being abietane diterpenoids the most prominent class. 8β-hydroxy-9(11),13-abietadien-12-one was identified in Hyptis for the first time. Hexane fraction was the most active against Bacillus subtilis, isolated compounds were also active against B. subtilis. The high activity of the hexane fraction is probably due to its major composition of abietane diterpenoids, class of compounds with renowned activity against Gram-positive bacteria. Results point out to a potential antibacterial activity of Hyptis lacustris against Gram-positive bacteria, mainly its Hexane fraction.