Costus species: natural pharmacological agents

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In India, the sacred Vedas provide many references on the utilities and importances of medicinal plants (Behera et al., 2008). Plant materials are of wide use in traditional systems of medicine, particularly in communities of the developing world. Medicinal plants are the native heritage of many distinctive geographical area and they bear significant global importances (Sukhdev et al., 2006). Wild edible tuber species are important sources of food in India and they play  significant role in the dietary habits of small and marginal families and forest- dwelling communities, most often during periods of food scarcity (Arora and Pandey 1996). Wild edible tubers refer to species that are neither cultivated nor domesticated, but available from their natural habitat and used as sources of food (Beluhan et al., 2010). Tubers, rhizomes and wild edible plants are collected and consumed from time to time by tribal and rural people over a period of 4-5 months from May- June to September- October to meet their food needs during periods of food shortage (Mishra et al., 2013). Edible tubers and rhizomes not only enrich the diet of the people but also possess medicinal properties. The use of plant based drugs and chemicals for curing various ailments and diseases are as old as human civilization. They are the only resources available for the treatment of different microbial infections among many rural and tribal communities even today . (Fischbash and Walsh, 2009).

              In Odisha, several tribal communities like Kharia, Kolho, Santhal and Mankirdia depend on wild food plants using their fruits, flowers, leafs, bulbils, tubers etc. as food for their daily requirement and also during the periods of food shortage and famine (Kumar et al., 2012). Tribals are fond of tuber crops and many of the forests are  rich in wild tubers which are used both for food and medicinal purposes (Nedunchezhiyan et al., 2012). Many tropical tuber species are used in the preparation of stimulants, tonics, carminatives and expectorants (Edison et al., 2006). The tuber crops like Ipomoea spp., Colocasia spp. Manihot spp., Dioscorea spp., Amorphophallus spp. and other rhizomatous crops like Curcuma spp., Costus spp., Zingiber spp.etc.  are profoundly used by the tribal communities of Odisha as food and medicines (Mishra et al., 2013). The genus Costus belonging to the family Costaceae has species like Costus igneus, Costus afer, Costus pictus, Costus arabicus, Costus dubius, Costus speciosus, etc. Among these species, Costus speciosus is profusely available in the forests of Odisha.  It is locally known as Kakaiya, keu, keukand. C. speciosus is widely used as therapeutic both in traditional and folk medicines (Saraf, 2010). Costus spp. are not only used as therapeutic medicines but for other socio- cultural purposes, such as wrapping of indigenous food items, mat making, treatment of evil repellants (Omukhua, 2011). The rhizome of Costus is used as an antifertility agent as it is rich in diosgenin, a suitable component for the synthesis of corticosteroids and oral contraceptives (Choudhury et al., 2012). The rural and tribal people use the leaves against ear infections, diarrhea, cold, catarrhal fever, cough, dyspepsia and rhizomes for skin diseases and snake bites (Ariharan et al., 2012). Costus sps. exhibit antibacterial activity due to the presence of phytochemical compounds like alkaloids, terpenoids, tannins, glycosides and saponins (Vasantharaj et al., 2013).

              The Genus Costus have long fleshy stem with tuberous rootstock. The leaves are spirally arranged with silky pubescent beneath. Flowers are densely arranged which are terminal or spikes. The Calyx is like short tube, funnel-shaped with ovate teeth. Corolla tube is short, the segments are large and sub equal. Stamens with broad filament, forming oblong petaloid process with the connective. The ovary is generally 3- celled, style is filiform and stigma with a semilunar ciliated depression. Ovules are many and superposed. Capsule globose or ovoid. Seeds are subglobose or obovoid with short aril (Haines, 1988). Flowering time of the plant is from August to October (Bhuyan et al., 2013). The genus Costus comprises of 175 species distributed in the humid tropics of both hemispheres. This genus is found in Indo-China, Malaysia to New Guinea, Taiwan and more or less throughout India (Saxena and Brahmam, 1994- 96). The plant is generally found in roadside ditches and low lying areas in the forests. It occurs throughout the foot hills of Himalayas from Himachal Pradesh to Assam, Vindhya Satpura hills in Central India, Eastern Ghats of Andhra Pradesh and Western Ghats of Maharashtra, Karnataka, Tamil Nadu and Kerala upto an altitude of 1220 ft (Sarin et al., 1974). Costus speciosus is the only species of family Costaceae found in Odisha. It is found in different parts of Odisha like Papadahandi, Gandhamardan, Jagatsinghpur, Cuttack, Rayagarh, Khurda etc. (Saxena and Brahmam, 1994- 96).

                                                Rhizome of Costus spp. is rich in macronutrients like carbohydrate, starch, amylose, protein, lipid etc. and also good source of micronutrients like Vitamin A. Besides it is rich in antioxidant, like β- carotene, ascorbic acid (Vitamin C), tocoferol (Vitamin E), that can prevent coronary disorder and cancer (Nedunchezhiyan et al., 2012). Singh (2011) reported the tubers of C. speciosus. are consumed raw or as vegetable. It is highly nutritious with  high content of carbohydrate- (44.51%), starch- (31.65%), amylose- (14.44%), protein- (19.20%) and lipid/oil (3.52%). The stem of Costus afer Ker Grawl. is reported to contain moisture (33.6%), crude fat (2.48%), crude protein (14.02%), carbohydrate (20.14%), crude fibre (15.55%) and ash (14.21%) which indicates its nutritional aspects (Ukana et al., 2012). Vishalakshi and Urooj (2010) reported that the leaves of C.speciosus and C. igneus contain 18 and 15.3% protein, 46 and 120mg iron, 81 and 216mg ascorbic acid, 660 and 1833μg β- carotene, 149 and 25mg α- tocopherol, 75 and 400mmol of GSH and 0.848 and 1.89mg/gm extract of total flavonoids respectively thus, the data revealed that both the plants are good sources of nutrients and natural antioxidant components. Karthikeyan et al., (2012) highlighted the protein and phenolic content of C.speciosus qualitatively and quantitatively and found that high amount of phenolic content was found in the mature leaf of the plant.  Antinutrients are natural or synthetic compounds that interfere with the absorption of nutrients. Protease inhibitors, lipase, amylase, phytic acid, oxalic acid etc. are some of the antinutrients. Ukana et al., (2012) reported the presence of phytochemicals in the stem of Costus afer with low toxicity level is beneficial in the field of agriculture and folk medicine. The anti- nutrients evaluated (in mg/ 100gm) were total oxalate (314.00), soluble oxalate (200.44), cyanide (24.40) and tannins (7.92). The saponins collected from Costus species observed to impair the digestion of protein and the uptake of vitamins and minerals in the gut of animals (Francis et al., 2002). Trace elements are the dietary elements that are needed in minute quantities for the proper growth, development and physiology. Singh (2011) reported the tubers of Costus speciosus are rich in minerals like Nitrogen, Calcium, Potassium etc. The tuber contains 3.14% Nitrogen, 1.72% Calcium, 1.42% Potassium, 0.28% Sodium, 0.19% Magnesium and 0.06% Phosphorus. Ukana et al., (2012) determined the mineral elements in the stem of Costus afer, which showed the presence of minerals (in mg/ 100g) like Potassium (88.00), Sodium (1.94), Calcium (200.40), Magnesium (191.39) and Phosphorus (6.02). Bioactive compounds are the compounds or the secondary plant metabolites eliciting pharmacological or toxicological effects. The rhizome of Genus Costus is very rich with well known compound Diosgenin Gupta et al., 2008. The rhizome is also rich with prosapogenin B of dioscin, diosgenone, cycloartanol, 25- en cycloartenol octacosanoic acid, spirostanol glycoside, (steroidal saponin) and furostanol glycoside 26-O-β- glucosidase (Rathore and Khanna, 1979; Inoue and Ebizuka, 1996). The rhizome and roots of Costus spp. contain 5α- stigmasten-3b-ol, sitosterol-β-D-glucoside, dioscin, prosapogenins A and B of dioscin, gracillin and quinines (Shrivastava et al., 2011).

Duraipandiyan et al. (2012) isolated two sesquiterpene lactones- costunolide and eremanthin from hexane extract of Costus speciosus which inhibited tested pathogens at lowest concentrations. The possible mechanism of action of Costunolide is that it stimulated the beta islets to secrete insulin by inhibiting the expression of nitric oxide synthase. It has been shown that costunolide inhibited the expression of nitric oxide synthase and thus helped in correcting the secretary defects in diabetes (Achrekar et al. 1991). Saraf (2010) reported the in vitro antibacterial activity of the rhizome of Costus speciosus. The species has shown efficient results against the bacterial strains like E. coli, S. aureus, K. pneumoniae and P. aeruginosa. The mature leaves of C. igneus have proven to be effective against bacterial pathogens like B. subtilis, P. mirabilis, E. coli, P. aeruginosa. The methanol extract showed maximum zone of inhibition against E. coli whereas  least zone of inhibition against P. mirabilis (Vasantharaj et al., 2013). Rhizome extract of C. speciosus was found to be most active against S. epidermidis and S. typhimurium. Thus, it is used as a potential bio- bacterialcide (Ariharan et al., 2012). The antibacterial activity of the different parts (leaf, flower, stem and root) of C. pictus exhibited pronounced activity against S. flexneri, K. pneumoniae, B. subtilis and E. coli. (Majumdar and Parihar, 2012).  Duraipandiyan et al. (2012) isolated two sesquiterpene lactones- costunolide and eremanthin from hexane extract of Costus speciosus which showed significant antifungal activity, the MIC values of costunolide were; 62.5 μg/ml against T. mentagrophytes, 62. μg/ml against T. simii, 31.25 μg/ml against T. rubrum, 125 μg/ml against E. floccosum, 250 μg/ml against Scopulariopsis spp., 250 μg/ml against A. niger, 125 μg/ml against C. lunata, 250 μg/ml against M. grisea. The ethyl acetate extract of C. speciosus rhizome and leaves has shown promising antifungal activity against fungal strains like T. rubrum, T. mengagrophytes, T. simii, E. floccosum, A. nizer, B. cinerea, C. lunata and C. albicans (Duraipandiyan and Ignacimuthu, 2011). The methanol extract of C. speciosus leaves exhibited inhibition against fungal strains like Penicillium spp. and Mucor spp. Thus, the plant possesses effective antifungal activity (Vasantharaj et al., 2013). The extracts of different parts of two species of Costus – Cheilocostus speciosus and C. pictus was found effective against fungus P. aphanidermatum whereas not effective against two fungi C. capsici and S. rolfsii (Abirami et al., 2014). Diabetes mellitus is a chronic metabolic disorder affecting approximately 4% population worldwide and is expected to increase to 5.4% in 2025 (Ignacimuthu 2008). Diabetes mellitus is a chronic disease characterized by high blood glucose levels due to absolute or relative deficiency of circulating insulin levels (Vishalakshi and Urooj 2008). Eliza et al.(2008) found that freeze-dried rhizome juice of C. speciosus had antidiabetic and hypolipidemic effect on body weight, liver and kidneys of normal and STZ-induced diabetic rats. The hexane crude extract of C. speciosus rhizome was effective in decreasing the serum glucose level and normalizing other biochemical parameters in diabetic rats. Aqueous extract and methanolic extracts of C. speciosus were highly effective in bringing down the blood glucose level (Rajesh et al. 2009). Daisy et al. (2008) investigated the possible protective effects of C. speciosus rhizome extracts on biochemical parameters in Streptozotocin (STZ)-induced male diabetic Wistar rats. STZ treatment (50 mg/kg) caused a hyperglycemic state that led to various physiologic and biochemical alterations. Hexane, ethyl acetate and methanol crude extracts administered at the dose of 250 mg/kg and 400 mg/kg respectively for 60 days to STZ-induced hypoglycemic and normo-glycemic rats. Kalailingam et al, (2011) investigated antihyperglycemic and hypolipidemic activities of methanol extract of C. igneus rhizome in Streptozotocin (STZ) induced diabetic albino rats. The results showed that fasting blood glucose, serum TC, TG, LDL, VLDL levels were significantly (p˂0.05) decreased, whereas serum HDL level was significantly(p˂0.05) increased in the diabetic rats.

Bavara et al. (2008) evaluated the antihyperglycemic, antihyperlipemic and antioxidant potency of ethanol extract of C. speciosus root in alloxan-induced diabetic male rats. C. speciosus is known to possess anti- diabetic properties and used in local health traditions in India (Rajesh et al., 2009). The methanol extract of  C. pictus leaves when administered as single dose per day to diabetes- induced rats for 21 days elicited significant (p<0.001) reductions of blood glucose, thus C. pictus leaf is a good anti- diabetic agent (Jothivel et al., 2007).