Electrocardiography effects of Abelmoschus esculentus fruit extract and its isolated compounds using isolated frog heart perfusion

This study evaluated the electrocardiograph effects of Abelmoschus esculentus and its isolated compounds on Rana temporaria (frog) heart. Cardiovascular disease is one of the major causes of mortality which contribute to about 57 million deaths as disclosed by WHO in 2002. There have been many therapeutic approaches to reduce the death rate from cardiovascular disease which include the use of herbal drugs from plants. The whole fruit of Abelmoschus esculentus (Okra) fruit has been used for culinary purposes in Africa. Medicinal properties of Abelmoschus esculentus reported in literature include its use as anti-diabetics, antimicrobial, diuretic agent, and for plasma replacement. However, there have been little or no report on the cardiovascular activities of the extract or isolated compounds from A. esculentus.

A. esculentus (Okra) fruits were collected, identified, dried, and powdered. The powdered was extracted using cold maceration with 100% methanol for 72 hours. The crude extract was subjected to repeated fractionation to isolate four (4) compounds. The cardiovascular activities of the crude extract and its isolated compounds were investigated using isolated heart perfusion technique on Rana temporaria (frog) heart. The effects of the extract and isolated compounds on the rate (frequency) and force of contraction (amplitude) of the heart beat were evaluated.

The isolated compounds were subjected to spectroscopic analysis using ultraviolent (UV), nuclear magnetic resonance (NMR) (1D and 2D experiments), and mass spectrometry. The compounds were elucidated as quercetin glycoside, quercetin diglycoside, urs-12-ene-3-O-β-D-glucopyranoside and 3-hydroxy-2,3-dihydroimidazo [1,5-a] pyridin-8(5H)-one-5-β-glucopyranoside (esculentoside). The extract and the isolated compounds showed positive inotropic effect on the heart (increase in amplitude of the heart) while they all also possess negative chronotropic effect (decrease in frequency) except compound 4 which possess positive chronotropic effect.

This study isolated three different classes of compounds from A. esculentus namely Flavonoids (Quercetin glycoside), Triterpene (Ursolic acid) and pyridine-imidazole (esculentoside). This study also demonstrated that A. esculentus extract and compounds isolated from it has negative chronotropic effects and also possess positive inotropic effects on the heart of R. temporaria.