Role of K[sup.+] and Ca[sup.2+] Channels in the Vasodilator Effects of Plectranthus barbatus (Brazilian Boldo) in Hypertensive Rats

• Published in: Cardiovascular therapeutics 2023-11, Vol.2023
• Main Authors: Moser, Jeniffer Cristóvão, da Silva, Rita de Cássia Vilhena, Costa, Philipe, da Silva, Luisa Mota, Cassemiro, Nadla Soares, Gasparotto Junior, Arquimedes, Silva, Denise Brentan
• Format: Article
• Language: English
• Subjects: Blood vessels; Calcium channels; Dilatation; Drug therapy; Enzyme inhibitors; Enzymes; Hepatitis B; Hypertension; Isoflavones; Medical research; Medicine, Experimental; Nitric oxide; Organic acids; Vasodilators
• ISSN: 1755-5914
• DOI: 10.1155/2023/9948707

Plectranthus barbatus, popularly known as Brazilian boldo, is used in Brazilian folk medicine to treat cardiovascular disorders including hypertension. This study investigated the chemical profile by UFLC-DAD-MS and the relaxant effect by using an isolated organ bath of the hydroethanolic extract of P. barbatus (HEPB) leaves on the aorta of spontaneously hypertensive rats (SHR). A total of nineteen compounds were annotated from HEPB, and the main metabolite classes found were flavonoids, diterpenoids, cinnamic acid derivatives, and organic acids. The HEPB promoted an endothelium-dependent vasodilator effect (~100%; EC50 ~347.10μ g/mL). Incubation of L-NAME (a nonselective nitric oxide synthase inhibitor; EC50 ~417.20μ g/mL), ODQ (a selective inhibitor of the soluble guanylate cyclase enzyme; EC50 ~426.00μ g/mL), propranolol (a nonselective α -adrenergic receptor antagonist; EC50 ~448.90μ g/mL), or indomethacin (a nonselective cyclooxygenase enzyme inhibitor; EC50 ~398.70μ g/mL) could not significantly affect the relaxation evoked by HEPB. However, in the presence of atropine (a nonselective muscarinic receptor antagonist), there was a slight reduction in its vasorelaxant effect (EC50 ~476.40μ g/mL). The addition of tetraethylammonium (a blocker of Ca[sup.2+]-activated K[sup.+] channels; EC50 ~611.60μ g/mL) or 4-aminopyridine (a voltage-dependent K[sup.+] channel blocker; EC50 ~380.50μ g/mL) significantly reduced the relaxation effect of the extract without the interference of glibenclamide (an ATP-sensitive K[sup.+] channel blocker; EC50 ~344.60μ g/mL) or barium chloride (an influx rectifying K[sup.+] channel blocker; EC50 ~360.80μ g/mL). The extract inhibited the contractile response against phenylephrine, CaCl[sub.2], KCl, or caffeine, similar to the results obtained with nifedipine (voltage-dependent calcium channel blocker). Together, the HEPB showed a vasorelaxant effect on the thoracic aorta of SHR, exclusively dependent on the endothelium with the participation of muscarinic receptors and K[sup.+] and Ca[sup.2+] channels.