Ravindra Semwal

The genus Stephania (Menispermaceae): Chemical and pharmacological perspectives

The plants of the genus Stephania (Menispermaceae) are widely distributed, and have long been used in folk medicine for the treatment of various ailments such as asthma, tuberculosis, dysentery, hyperglycemia, malaria, cancer and fever. Over 150 alkaloids together with flavonoids, lignans, steroids, terpenoids and coumarins have been identified in the genus, and many of these have been evaluated for biological activity. This review presents comprehensive information on the chemistry and pharmacology of the genus together with the traditional uses of many of its plants. In addition, this review discusses the structure-activity relationship of different compounds as well as recent developments and the scope for future research in this aspect.

Anti-hyperglycemic effect of 11-hydroxypalmatine, a palmatine derivative from Stephania glabra tubers.

A palmatine derivative, named 11-hydroxypalmatine (4), has been isolated from the tubers of Stephania glabra, together with three known alkaloids, palmatine (1), dehydrocorydalmine (2), and stepharanine (3). The structures of the compounds were elucidated by means of spectroscopic analysis including 2D NMR experiments. The hypoglycemic activity of 4 was evaluated against alloxan-induced diabetic mice. The test compound was administered at doses of 25, 50, and 100 mg/kg, p.o., 36 h after alloxan injection (60 mg/kg, i.v.). The alloxan-induced diabetic mice showed significant reduction in blood glucose after treatment with the test compound by 52% as compared to the positive control glibenclamide (54%) and the diabetic control (27%).

Recent trends in oral transmucosal drug delivery systems: an emphasis on the soft palatal route

Introduction: The oral mucosa is an appropriate route for drug delivery systems, as it evades first-pass metabolism, enhances drug bioavailability and provides the means for rapid drug transport to the systematic circulation. This delivery system offers a more comfortable and convenient delivery route compared with the intravenous route. Although numerous drugs have been evaluated for oral mucosal delivery, few of them are available commercially. This is due to limitations such as the high costs associated with developing such drug delivery systems. Areas covered: The present review covers recent developments and applications of oral transmucosal drug delivery systems. More specifically, the review focuses on the suitability of the oral soft palatal site as a new route for drug delivery systems. Expert opinion: The novelistic oral soft palatal platform is a promising mucoadhesive site for delivering active pharmaceuticals, both systemically and locally, and it can also serve as a smart route for the targeting of drugs to the brain.

Chemical constituents from the leaves of Boehmeria rugulosa with antidiabetic and antimicrobial activities.

Three new flavonoid glycosides, named chalcone-6′-hydroxy-2′,3,4-trimethoxy-4′-O-β-d-glucopyranoside (1), isoflavone-3′,4′,5,6-tetrahydroxy-7-O-{β-d-glucopyranosyl-(1 → 3)-α-l-rhamnopyranoside} (2), and isoflavone-3′,4′,5,6-tetrahydroxy-7-O-{β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosyl-(1 → 3)-α-l-rhamnopyranoside} (3), were isolated from the leaves of Boehmeria rugulosa, together with five known compounds, β-sitosterol, quercetin, 3,4-dimethoxy-ω-(2′-piperidyl)-acetophenone (4), boehmeriasin A (5), and quercetin-7-O-β-d-glucopyranoside. The structures of the isolated compounds were determined by means of chemical and spectral data including 2D NMR experiments. The ethanolic extract of leaves showed significant hypoglycemic activity on alloxan-induced diabetic mice. Glibenclamide, an oral hypoglycemic agent (5 mg/kg, p.o.), was used as a positive control. The ethanolic extract of the plant as well as the isolated compounds 1–3 (25 μg/ml) showed potent antimicrobial activity against two bacterial species (Staphylococcus aureus and Streptococcus mutans) and three fungus pathogens (Microsporum gypseum, Microsporum canis, and Trichophyton rubrum). The activities of the isolated compounds 1–3 have been compared with positive controls, novobiocin, and erythromycin (15 μg/ml).

Analgesic and Antipyretic Activities of Gindarudine, a Morphine Alkaloid from Stephania glabra

Gindarudine (GN), a morphine alkaloid isolated from the tubers of Stephania glabra (Menispermaceae), was evaluated for analgesic and antipyretic activities because of closely resembling structure to that of thebaine. The analgesic activity of GN was evaluated on albino mice by hot plate and tail immersion methods whereas antipyretic activity was studied on Brewers yeast-induced pyrexia rats. Fever was induced by injecting 20 ml/kg (s.c.) of 20% aqueous suspen- sion of Brewers yeast in normal saline and rectal temperature was recorded by clinical thermometer immediately before (- 18 h) and 18 h after (0 h) yeast administration. GN at doses of 100 and 150 mg/kg, p.o. showed significant analgesic ac- tivity (p<0.05) by increasing the threshold potential of pain whereas doses of 200 and 300 mg/kg exhibited significant (p<0.05) antipyretic effect by decreasing the rectal temperature of rats in 1 st , 3 rd and 5 th h after treatment. Aspirin (300 mg/kg, p.o.) and paracetamol (200 mg/kg, p.o.) were used as standard drugs for analgesic and antipyretic activities respec- tively. These findings demonstrate that GN have remarkable analgesic and anti-pyretic activities when compared with positive control and thus have great potential as a source for natural health products.

A gastroretentive drug delivery system of lisinopril imbibed on isabgol-husk.

The gastroretentive drug delivery system is site-specific and allows the drug to remain in the stomach for a prolonged period of time so that it can be released in a controlled manner in gastrointestinal tract. The present study was carried out to develop a gastroretentive drug delivery system using isabgol as an excipient to prolong the residence time of the model drug lisinopril in the stomach. The gastroretentive ability of isabgol was increased by addition of NaHCO3 as a gas-generating agent while its mucoadhesive property was enhanced by incorporation of HPMC-K4M. The drug, NaHCO3 and HPMC-K3M were imbibed on isabgol-husk as per entrapment efficiency of the isabgol-husk. After drying, the product was filled in a hard gelatin capsule and evaluated for its buoyancy, mucoadhesive properties, swelling index and in vitro drug release. The lisinopril released through isabgol was delayed by 12 hours when compared to a preparation available on the market which released the complete drug in 0.5 hours. The drug release study of lisinopril from the formulation follows first order kinetics using a diffusion controlled mechanism. The results from the present study revealed that isabgol can be used as a potential excipient for the formulation of gastroretentive drug delivery systems in the near future.