Annona squamosa seed extract in the regulation of hyperthyroidism and lipid-peroxidation in mice: possible involvement of quercetin.

Abstract

Annona squamosa (Custard apple) seeds are generally thrown away as waste materials. The extract of these seeds was evaluated for its possible ameliorative effect in the regulation of hyperthyroidism in mouse model. Serum triiodothyronine ([T.sub.3]), thyroxine ([T.sbu.4]) concentrations, hepatic glucose-6-phospatase (G-6-Pase) and 5'-mono-deiodinase (5'DI) activity were considered as the end parameters of thyroid function. Simultaneously hepatic lipid peroxidation (LPO), superoxide dismutase (SOD) and catalase (CAT) activities were investigated to observe its hepatotoxic effect, if any.

L-[T.sub.4] administration (0.5 mg/kg/d for 12 days, i.p.) increased the levels of serum [T.sub.3] and [T.sub.4], activity of hepatic G-6-Pase, 5'DI and LPO with a parallel decrease in SOD and CAT activities. However, simultaneous administration of the Annona seed extract (200 mg/kg) or quercetin (10mg/kg) to [T.sub.4]-induced hyperthyroid animals for 10 days, reversed all these effects indicating their potential in the regulation of hyperthyroidism. Further, the seed extract did not increase, but decreased the hepatic LPO suggesting its safe and antiperoxidative nature. Quercetin also decreased hepatic LPO. When relative efficacy was compared with that of propyl thiouracil (PTU), a standard antithyroidic drug, experimental seed extract appeared to be more effective. Phytochemical analyses including HPLC revealed the presence of quercetin in the seed extract and the results on the effects of quercetin suggested the involvement of this phytochemical in the mediation of antithyroidal activity of Annona squamosa seed extract.

[c] 2006 Elsevier GmbH. All rights reserved.

Keywords: Annona squmosa seed extract; HPLC analyses; Hyperthyroidism; Lipid peroxidation; Quercetin

Introduction

Thyroid hormones regulate almost all functional aspects of the body, including metabolic, respiratory, cardiovascular, nervous and reproductive functions, either directly or indirectly (Ganong, 1995). Alterations in the level of these hormones lead not only to altered basal metabolic rate but also to many health problems. Particularly, hyperthyroidism (chronic elevated circulatory thyroid hormones), if not treated properly, some times ends up with the common health problems such as diabetes mellitus and cardio-vascular diseases (Fry, 1993).

Despite the fact that plant-based drugs are gradually becoming the choice of the patients for their safe and economic nature, on herbal regulation of hyperthyroidism scientific investigations are meager (Tahiliani and Kar, 2003; Kar and Panda, 2004). Although Annona seeds are generally thrown away as waste materials, they are known to possess insecticidal, anti-ovulatory, abortifacient and anti-implantation properties (Vohora et al., 1975; Rao et al., 1979; Damasceno et al., 2002). In the present study an attempt has been made to reveal its hitherto unknown ameliorative efficacy, if any, in the regulation of hyperthyroidism using laboratory mouse as working model. Attempt has also been made to correlate the thyroid regulating activity of Annona squamosa seed with its major active component, quercetin by undertaking the phytochemical studies, including its quantification by HPLC and then comparing its effects with that of seed extract.

Materials and methods

Plant materials

Clean and good quality seeds of uniform size, from ripe A. squamosa (Annonacae) fruits were collected locally. After identification, the voucher specimen (No. AS/02) was deposited in the …