Selective bronchodilatory effect of Rooibos tea (Aspalathus linearis) and its flavonoid, chrysoeriol
- First Online:
Rooibos tea (Aspalathus linearis) is commonly used for hyperactive gastrointestinal, respiratory and cardiovascular disorders.
Aim of study
The aqueous extract of Rooibos tea (RT) was studied for the possible bronchodilator, antispasmodic and blood pressure lowering activities in an attempt to rationalize some of its medicinal uses.
Isolated tissue preparations, such as rabbit jejunum, aorta and guinea-pig trachea and atria were set up in appropriate physiological salt solutions and aerated with carbogen. For in vivo studies rats were anesthetized with pentothal sodium and blood pressure was measured through carotid artery cannulation.
In jejunum, RT caused a concentration-dependent relaxation of low K+ (25 mM)-induced contractions, with mild effect on the contractions induced by high K+ (80 mM). In presence of glibenclamide, the relaxation of low K+-induced contractions was prevented. Similarly, cromakalim caused glibenclamide-sensitive inhibition of low K+, but not of high K+, while verapamil did not differentiate in its inhibitory effect on contractions produced by the two concentrations of K+. Like in jejunum, RT caused glibenclamide-sensitive relaxation of low K+-induced contractions in trachea and aorta, but with a 20 times higher potency in trachea. In atria, RT was least potent with weak inhibitory effect on atrial force and rate of contractions. RT caused a dose-dependent fall in arterial blood pressure in rats under anesthesia. Among the tested pure compounds of Rooibos, chrysoeriol showed selective bronchodilator effect. Chrysoeriol (luteolin 3′-methyl ether) is a bioactive flavonoid known for antioxidant, antiinflammatory, antitumor, antimicrobial, antiviral, and free radical scavenging activities.
These results indicate that the bronchodilator, antispasmodic and blood pressure lowering effects of Rooibos tea are mediated predominantly through KATP channel activation with the selective bronchodilatory effect. This study provides a sound mechanistic basis for the wide medicinal use of Rooibos tea, with the therapeutic potential to be developed for congestive respiratory ailments.
KeywordsRooibos tea KATP channel activator airway selectivity hypotensive chrysoeriol
- 1.Wyk BV, Oudtshoorn BV, Gericke N (2002) Medicinal plants of South Africa. Briza Publications, Pretoria, pp 48–49Google Scholar
- 2.Wesgro background report (2000) The Rooibos industry in the Western Cape. WESGRO, Western Cape investment and trade promotion agency, Cape Town, http://www.wesgro.org.za
- 4.Duke JA, Bogenschutz-Godwin MJ, Du celliar J, Duke PAK (2002) Hand book of medicinal herbs, 2nd edn. CRC Press, Boca Raton, pp 612–613Google Scholar
- 5.Brown D (1995) Encyclopaedia of herbs and their uses. Dorling Kindersley, London, p 244Google Scholar
- 6.Nakano M (1997) Rooibos tea as an anti-aging beverage. Rooibos Limited, Clanwilliam, 8135Google Scholar
- 9.Ulicna O, Vancova O, Bozek P, Carsky J, Sebekova K, Boor P, Nakano M, Greksak M (2006) Rooibos tea partially prevents oxidative stress in streptozotocin-induced diabetic rats. Physiol Res 55:157–164Google Scholar
- 10.Na HK, Mossanda KS, Lee JY, Surh YJ (2004). Inhibition of phorbol ester-induced COX-2 expression by some edible African plants. Biofactors 21:149–153Google Scholar
- 12.National Research Council (1996) Guide for the care and use of laboratory animals. National Academy Press, Washington, pp 1–7Google Scholar
- 13.Evans WC (1996) Trease and Evan’s pharmacognosy, 14th edn. WB Sounders, London, pp 161–408Google Scholar
- 15.Huang DJ, Lin CD, Chen HJ, Lin YH (2004) Antioxidant and antiproliferative activaties of sweet potato (Ipomoea batatas [L.] Lam ‘Tainong 57’) constituents. Bot Bull Acad Sin 45:179–186Google Scholar
- 20.Hamilton TC, Weir SW, Weston TH (1986) Comparison of the effects of BRL34915 and verapamil on electrical and mechanical activity in rat portal vein. Br J Pharmacol 88:103–111Google Scholar
- 21.Aguilar-Bryan L, Clement JP, Gonzalez G, Kunjilwar K, Babenko A, Bryan J (1998) Towards understanding the assembly and structure of KATP channels. Physiol Rev 78:227–245Google Scholar
- 23.Revuelta MP, Cantabrana B, Hidalgo A (1997) Depolarization-dependent effect of flavonoids in rat uterine smooth muscle contraction elicited by CaCl2. Gen Pharmacol 29:847–857Google Scholar
- 24.Sanchez de Rojas, Somoza VR, Ortega BT, Villar AM (1996) Isolation of vasodilatory active flavonoids from the traditional remedy Satureja obovata. Planta Med 62:272–274Google Scholar
- 25.Ripoll C, Lederer WJ, Nichols CG (1990) Modulation of ATP-sensitive K+-channel activity and contractile behavior in mammalian ventricles by the potassium channel openers: cromakalim and RP49356. J Pharmacol Exp Ther 255:429–435Google Scholar
- 26.Osterrieder W (1988) Modefication of K+ conductance of heart cell membrane by BRL 34915. Naunyn Schmiedeberg’s Arch Pharmacol 33:93–97Google Scholar
- 27.McPherson GA, Angus JA (1990) Characterization of responses to cromakalim and pinacidil in smooth and cardiac muscle by use of selective antagonists. Br J Pharmacol 100:201–206Google Scholar
- 28.Tong X, Porter LM, Liu G, Chowdhury PD, Srivastava S, Pountney DJ, Yoshida H, Artman M, Fishman GI, Yu C, Iyer R, Morley GE, Gutstein DE, Coetzee WA (2006) Consequences of cardiac myocyte-specific ablation of KATP channels in transgenic mice expressing dominant negative Kir6 subunits. Am J Physiol Heart Circ Physiol 291:H543–H551CrossRefGoogle Scholar