Abstract
BackgroundThe aqueous-methanolic extract of Amaranthus spinosus (A. spinosus Linn.,) whole plant, was studied for its laxative, spasmolytic and bronchodilator activities to validate some of its medicinal uses.MethodsThe crude extract of A. spinosus was studied in-vivo for bronchodilator and laxative activities and in-vitro using isolated tissue preparations which were mounted in tissue baths assembly containing physiological salt solutions, maintained at 37°C and aerated with carbogen, to assess the spasmolytic effect and to find out the possible underlying mechanisms.ResultsIn the in-vivo experiments in mice, the administration of A. spinosus increased fecal output at doses of 100 and 300 mg/kg showing laxative activity. It also inhibited carbachol-induced bronchospasm in anesthetized rats at 1, 3, 10 and 30 mg/kg indicative of bronchodilator activity. When tested on isolated gut preparations, the plant extract showed a concentration-dependent (0.01-10.0 mg/ml) spasmogenic effect in spontaneously contracting rabbit jejunum and guinea-pig ileum. The spasmogenic effect was partially blocked in tissues pretreated with atropine (0.1 μM). When tested on K+ (80 mM)-induced sustained contractions in isolated rabbit jejunum, the plant extract caused complete relaxation and also produced a shift in the Ca++ concentration-response curves (CRCs) towards right, similar to diltiazem. In rabbit trachea, the plant extract completely inhibited K+ (80 mM) and carbachol (CCh, 1 μM)-induced contractions at 1 mg/ml but pretreatment of tissue with propranolol (1 μM), caused around 10 fold shift in the inhibitory CRCs of the plant extract constructed against CCh-induced contraction. The plant extract (up to 0.3 mg/ml) also increased both force and rate of spontaneous contractions of isolated guinea-pig atria, followed by relaxation at higher concentration (1.0-5.0 mg/ml). The cardio-stimulant effect was abolished in the presence of propranolol, similar to that of isoprenaline. Activity-directed fractionation revealed that the spasmolytic component(s) was separated in the organic fraction, whereas the spasmogenic component was concentrated in the aqueous fraction.ConclusionThese results indicate that A. spinosus possesses laxative activity partially mediated through cholinergic action. The spasmolytic effect was mediated through calcium channel blocking (CCB), while bronchodilator activity through a combination of β-adrenergic and CCB pathways, which may explain the traditional uses of A. spinosus in gut and airways disorders.
Highlights
The aqueous-methanolic extract of Amaranthus spinosus (A. spinosus Linn.,) whole plant, was studied for its laxative, spasmolytic and bronchodilator activities to validate some of its medicinal uses
The laxative effect of the plant extract was declined with further increase in dose to 500 mg/kg
Inhibitory effect of A. spinosus was comparable to aminophylline, used as a positive control, which inhibited the CCh-mediated bronchoconstriction at similar doses by 13.3 ± 5.8, 30.5 ± 4.5, 42.8 ± 10.6 and 54.1 ± 5.2% (n = 4), respectively (Figure 2b)
Summary
The aqueous-methanolic extract of Amaranthus spinosus (A. spinosus Linn.,) whole plant, was studied for its laxative, spasmolytic and bronchodilator activities to validate some of its medicinal uses. It is a popular medicinal plant reputed for antipyretic, appetizer, diuretic, febrifuge, galactagogue, haematinic, laxative and stomachic effects and as a treatment for hallucination, leprosy, eczema and piles [2]. It is useful in bronchitis, leucorrhoea, menorrhagia, boils, burns, nausea, flatulence and colic [4], healing of wounds and rheumatism [5], and to arrest the coughing up of blood [6]. Different studies have evaluated A. spinosus for the presence of antioxidant [7], antinociceptive [8], hepatoprotective [9], anti-diabetic, anti-hyperlipidemic, spermatogenic [10] and antimalarial [11] activities
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