The latex bearing plants Euphorbia antiquorum, E. antisyphilitica, E. caducifolia, E. neerifolia, E. nivulia, E. royleana, Calotropis procera, C. gigantea and Cryptostegia grandiflora, Plumeria alba,  Nerium indicum and Mimusops elengi were evaluated as potential renewable sources of energy crops for liquid fuels, non-polar constituents  and chemicals (Kumar and Kumar, 1984, Bhatia et al., 1984, Kumar, 2004). Plant leaf, stem, bark and also whole plants were analyzed for elemental composition, oil, polyphenol, hydrocarbons, crude protein, <?xml:namespace prefix = v ns = "urn:schemas-microsoft-com:vml" /><?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />-cellulose, lignin and ash. The dry weight of individual plant was  4.47 and 13.74 kg/plant (Kalita and Saikia, 2001). The carbon contents in whole plants varied from 38.5% to 44.9%, while hydrogen and nitrogen contents varied from 5.86% to 6.72% and 1.26% to 2.34%, respectively. The bark of the plants contained the highest amount of hydrocarbons (1.78–3.93%) and the leaves contained the lowest amounts (0.26–1.82%). The unsaponifiable materials and fatty acids in the oil fractions of whole plants ranged from 22.8% to 56.4% and 24.7% to 58.7%, respectively. The highest gross heat value was exhibited by C. procera (6145 cal/g) and the lowest by N. indicum (4405 cal/g). Hydrocarbon fractions were characterized by IR and ¹H-NMR and by thermogravimetric analyses. The activation energy (E_a) in the third stage of decomposition was the greatest in the hydrocarbon fraction obtained from M. elengi (16.40 kJ mol⁻¹) and the lowest for C. procera (3.96 kJ mol⁻¹). The study indicated that the plant species might be suitable as alternative source of hydrocarbons and other phytochemicals (Kalita and Saikia, 2001). 

The identification and cultivation of plants rich in hydrocarbons as renewable sources of chemicals for use as fuel and chemical feedstocks has generated considerable interest. (Nielsen et al., 1977; Buchanan et al., 1978a, 1978b; Calvin, 1978; Saxon, 1980; Wang and Huffman, 1981; Adams and McChesney, 1982; Campbell, 1983; Jenkins and Ebeling, 1985; Abbott et al., 1990; Seiler et al., 1991,  Kumar, 2004). The shortage and depletion of worldwide sources of fossil hydrocarbon warrants development of alternative sources of fuels and chemicals. There are thousands of plant species that produce copious amounts of hydrocarbons, and these hydrocarbon-bearing plants are a special group of shrubs and trees that are being identified and selected to initiate agronomic and genetic improvements (Paul, 1981; Campbell, 1983; Bhatia et al., 1984; Margaris and Vokou, 1985). Studies have been conducted on plant species containing hydrocarbons, which can be cultivated as fuel crops (Isely, 1981; Lipinsky, 1981; Adams and McChesney, 1982; Emon and Seiber, 1984; Roth et al., 1984; Carr, 1985; Carr et al., 1986; Carr and Bagby, 1987 Kalita and Saikia, 2000, Kumar, 2004). Besides this,  such plants have great pharmacological value and contain valuable compounds. A large number of plants have medicinal potential and screening and characterization of several plants has been done (Dhar et al., 1969). It is proposed to study the pharmacognostical properties of Calotropis procera and bio-prospecting of Calotropis procera during the investigations. 

Review of literature

Work done at National level:

Calotropis procera (Asclepiadaceae) is a wild shrub, which grows up to a height of 1-3 m and its leaves are 10–13 cm wide by 17–19 cm long. Calotropis procera (Ait.) R.Br. commonly known, as ‘Akra’ is a popular medicinal plant found throughout the tropics of Asia and <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Africa and is used in many traditional systems of medicine. Important factors of the various parts of this plant have been widely reported.

Calotropis procera latex has been used in leprosy, eczema, inflammation, cutaneous infections, syphilis, malarial and low hectic fevers, and as abortifacient ( Kumar and Basu, 1994).  Leaves: in rheumatism, as an anti-inflammatory and antimicrobial and Roots: as hepatoprotective agents, against colds and coughs, syphilis and elephantiasis, as an anti-inflammatory,  analgesic, antimalarial and antimicrobial. Flowers: as cytostatic, abortifacient, antimalarial, in asthma and piles and villagers in Bikaner district ingest almost all plant parts in various dietary combinations for malarial fevers and pyrexias (Sharma and Sharma, 2000).

The plant produces latex in the laticifers. It has been established that laticifer differentiation in vitro is a cytokinin-dependent process and among the cytokinins, FAP was more effective than BA and 2-iP. But the type of auxin and its concentration also play an important role in modifying the effect of cytokinin. Among the different auxins used IAA was more effective for laticifer differentiation than IBA and NAA, while 2,4D was inhibitory. Maximum laticifer differentiation (17·01% was observed on MS medium supplemented with 4·6 M FAP and 1 M IAA (Suri and Ramawat, 1995).

Dried latex and chloroform extract of roots has been reported to possess anti-inflammatory activity (Kumar and Basu,1994). Aqueous extract of the flowers has been found to exhibit analgesic, antipyretic and anti-inflammatory activity. The alcoholic extract from different parts has been found to possess antimicrobial and spermicidal activity (Kamatha et al.,  2002)

The anti-inflammatory property of the latex of Calotropis procera was studied on carrageenin- and formalin-induced rat paw oedema model. A single dose of the aqueous suspension of the dried latex was effective to a significant level against the acute inflammatory response (Basu and Nag Chaudhuri 1991, Kumar and Basu, 1994).

  A literature survey of Calotropis procera revealed that the plant contains mainly cardenolides besides steroids and triterpenes. From the hexane-insoluble fraction of this plant a new free cardenolide named proceragenin has been isolated. The medicinal importance of Calotropis procera prompted the studies on pharma-cological screening of the antibacterial and anti-aggregating activities of proceragenin (Akhtar, 1992).   Procesterol, a new steroidal hydroxy ketone, has been isolated from the fresh and undried flowers of Calotropis procera. The chemical and spectral studies identified it as a C-6 C-24 diepimer of stigmast-4-en-6 -ol-3-one (Khan et al.,1989).

Bast fibres of Calotropis procera (aak) plant have been separated by retting. The yarn of blend of cotton and aak in 1:1 proportion was inferior to cotton in respect of strength, fineness and evenness. The properties of cloth indicated that aak cloth has high tensile and abrasion strength and more weight per square metre than cotton cloth. The study suggested that good quality cloth could be prepared from aak yarn if its evenness and fineness are improved (Varshney and Bhoi 1987, 1988).

Mosquito control by Calotropis latex has been reported by Girdhar et al., (1984). The effect of crude fractions of C procera, its flower, bud and root were tested against a chloroquine sensitive strain, MRC 20 and a chloroquine resistant strain, MRC 76 of Plasmodium falciparum (Sharma and Sharma, 1999). 

The dry latex (DL) of Calotropis procera  (Asclepiadaceae), a potent anti-inflammatory agent has been evaluated for anti-diarrhoeal activity. Anti-diarrhoeal effects of C. gigantea used traditionally in Indian system of medicine were recorded.  The remarkable anti-diarrhoeal effect of C.gigantea extract against castor oil-induced diarrhoea model attests to its utility in a wide range of diarrhoeal states (Chitme et al.,  2004).

 Like atropine and phenylbutazone (PBZ), a single oral dose of DL (500 mg/kg) produced a significant decrease in frequency of defecation, severity of diarrhoea and afforded protection from diarrhoea in 80% rats treated with castor oil ( Kumar et al., 2001) .

Besides this, the plant contains several useful enzymes. A protease was purified to homogeneity from the latex of medicinal plant Calotropis procera  The molecular mass and isoelectric point of the enzyme are 28.8 kDa and 9.32, respectively. Hydrolysis of azoalbumin by the enzyme was optimal in the range of pH 7.0–9.0 and temperature 55–60 °C. The enzyme hydrolyses denatured natural substrates like casein, azoalbumin, and azocasein with high specific activity. Proteolytic and amidolytic activities of the enzyme were activated by thiol protease activators and inhibited by thiol protease inhibitors, indicating the enzyme to be a cysteine protease ( Dubey and Jagannadham 2003).

The role of antioxidants, which are thought to scavenge the oxygen-free radicals in plants exposed to relatively low concentrations of ambient air pollutants for long durations, was studied for a year. Increases were observed in superoxide dismutase peroxidase activity, sulphate and leaf area to dry weight ratio, and decreases in stomatal conductance, ascorbic acid, protein content and total lipids, as a general response of all the plants in the polluted area. The results indicate that high peroxidase activity in the control plants and enhanced superoxide-dismutase activity in the polluted area might have enhanced the ability of Cassia siamea to tolerate stress better than Dalbergia sissoo. Similarly, enhanced activities in the polluted sites made Calotropis procera more tolerant of stress than Ipomoea fistulosa. Thus, it appears that monitoring of antioxidant activities offers a useful tool in understanding the mechanisms which make plants relatively tolerant in field conditions (Rao and Dubey 1990). Thus the Calotropis procera plants are more tolerant to field stress conditions. 

Pretreatment with an ethanolic latex extract of Calotropis procera at a dose of 300 mg/kg body wt., administered orally thrice a day for 30 days, reduced significantly (p < 0.01) the elevated marker enzyme levels in serum and heart homogenates in isoproterenol-induced myocardial infarction. Histopathological observation revealed a marked protection by the extract in myocardial necrotic damage (Mueen et al., 2004).

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Calotropis procera is a bush latex plant, 1–3 m high;. This plant is very drought-resistant and grows throughout the Sahelian countries, notably in Burkina Faso. Batch fermentation experiments show that it is a good substrate for biogas production. The highest productivities obtained varied from 2·9 to 3·6 litres biogas day⁻¹ litre⁻¹ when the digester loading was a 4% (w/v) suspension of dry leaves at initial pH 7·5. The acidogenic step of the fermentation was very fast, about 66% of dry material loaded being degraded during the first 2 days of incubation at 30°C. The resulting biogas contained 56–59% (v/v) methane (Traore, 1992).

The Palestine mountains are covered yearly with a huge number of plant species. About 2300 species are condensed on this small Mediterranean area, out of which more than 700 species are mentioned in ethnoiatric data (Silva and Abraham, 1981; Shtayeh and Hamad, 1995). Many plant species have been used in folkloric medicine to treat various ailments of man (Palevitch and Yaniv, 1991).

According with the ethnobotanical literature a great number of medicinal plants are being used to treat microbial infections particularly in the rural areas of Yemen where the traditional folk medicine remains a major source to cure minor ailments (Awadh Ali et al., 2001). Up to date, very little research was done to investigate these traditionally used medicinal plants (El-Fiky et al., 1995). Calotropis procera has been shown to have antibacterial properties against three Gram-positive bacteria and two Gram-negative bacteria.

The decoction of the aerial part of Calotropis procera is commonly used in Saudi Arabian traditional medicine for the treatment of variety of diseases including fever, joint pain, muscular spasm and constipation. The ethanol extract of the plant were tested on laboratory animals for its antipyretic, analgesic, anti-inflammatory, antibacterial, purgative and muscle relaxant activities. The results of this study showed a significant antipyretic, analgesic and neuromuscular blocking activity. On smooth muscle of guinea pig ileum, the extract produced contractions which was blocked by atropine supporting its use in constipation. The extract failed to produce significant anti-inflammatory and antibacterial activities. Phytochemical studies on the aerial parts of C. procera showed the presence of alkaloids, cardiac glycosides, tannins, flavonoids, sterols and/or triterpenes. However, the chemical constituents responsible for the pharmacological activities remains to be investigated. The safety evaluation studies revealed that the use of extract in single high doses (up to 3 g/kg) does not produce any visible toxic symptoms or mortality. However, prolong treatment (90 days) causes significantly higher mortality as compared to control group Ethanolic extracts of 20 selected plant species used by Yemeni traditional healers to treat infectious diseases were screened for their antibacterial activity against both Gram-positive and Gram-negative bacteria, as well as for cytotoxic activity. Extracts of Calotropis procera, Chenopodium murale, Pulicaria orientalis, Tribulus terrestris and Withania somniferum displayed a remarkable activity (Mossa, 1991). In parts of West Africa, including Nigeria and the Republic of Benin, the juice from the leaves of the Sodom apple (Calotropis procera) is used for traditional cheese-making. Cheese-making with this juice is purely empirical and little is known about the properties of the juice and the mechanism of milk coagulation (Ogundiwin&Oke, 1983). Recently, a partially purified milk-clotting enzyme was extracted from Sodom apple leaves (Aworh & Nakai, 1986).  Calotropis procera has also been used for cheese making.  Chemical composition and texture profile of cheese made with vegetable rennet from Calotropis procera (sodom apple) leaves were compared with those of a direct acid cheese made with calf rennet. Relative to that made with calf rennet, cheese made with vegetable rennet was harder, less cohesive and more gummy, presumably because of differences in chemical composition and physical characteristics between the cheeses (Aworh and Muller 1987).