FIELD OF THE INVENTION The present invention relates to novel compositions for hair loss prevention and/or hair growth promotion comprising at least one agent preferably derived from natural source as active agent, either alone or in combination with other active agent(s), and at least one carrier, optionally with one or more other excipient(s). The active agent is preferably extracted from the plant Vernonia sp. The present invention also describes process for extraction of the hair growth promoting agent and also process of preparation of compositions comprising such active agent. Also the present invention provides method of using such compositions. The novel composition is in the form of an oral preparation such as tablet or capsule, or a topical preparation such as liquid solution or suspension, cream, gel, lotion or spray. The compositions are particularly useful against hair disorders and/or other associated disorders particularly in the management of testosterone induced androgenic alopecia. The compositions of the present invention are useful as a pharmaceutical or a cosmetic or an ayurvedic product. BACKGROUND OF THE INVENTION The use of herbal products for medicinal benefits has played an important role in nearly every culture on earth. Herbal medicine was practiced by ancient people in Africa, Asia, Europe, and the Americas. The recent increase in the use of herbal products is associated with the belief that herbs can provide some benefits over and above allopathic medicine and allows users to feel that they have some control in their choices of medications. In India particularly, Ayurveda is an example of a long standing tradition that offers a unique insight into approaches for the prevention and/or treatment of various human ailments. These herbal products are safe compared to allopathic drugs. Vernonia anthelmintica plant is cultivated by the Sri Lankans, and is in great repute as a remedy, which is indicated by its name. The bitter, nauseous, black seeds of this plant, in doses of 50 to 60 grains, are valued in Sri Lanka as an anthelmintic and are commonly used for expelling the Ascaris lumbricoides, and also as a vermicide. The dose of the powdered seed to an adult is from '/2 to 1 drachm. The native physicians prescribe it generally as a tonic in the shape of an infusion. The Sri Lankan name and the Tamil name of Vernonia anthelmintica is sanne nayan and kado-seragam respectively. The Vernonia plant is a small herb found all over India and its powdered seed is especially mixed with honey to expel intestinal worms, cough and indigestion. It is also commonly referred to as Iron weed and is a very common plant in the Western states, growing in the woods and prairies, and along river streams, and flowering from July to September. The root, which is the part used, is bitter, and imparts its properties to water or alcohol. Iron weed is a bitter tonic, deobstruent, and alterative. In powder or decoction, the root is beneficial in amenorrhoea, dysmenorrhoea, leucorrhoea, and menorrhagia. In intermittent, remittent and bilious fevers, the decoction or a saturated tincture has been recommended. It is also said to have been useful in scrofula, and some cutaneous diseases. Dose of the decoction is usually 1 to 2 fluid ounces; of the tincture, 1 to 2 fluid drachms. The leaves or powdered root in the form of poultice make an excellent discutient application to tumors. Several species of the plant Vernonia such as Vernonia noveboracense, Willdenow, and its variety, V. praealta, bearing purple flowers, and the V. tomentosa, with some other species possess similar medicinal properties as Vernonia anthelmintica. The root of V. nigritiana, Oliver, of West Africa, is used in Senegambia, under the name of batiatior, as a febrifuge. It contains the glucoside namely vernonin (Heckel and Schlagdenhauffen, Amer. Jour. Pharm., 1889, p. 40). Vernonia belongs to the Asteraceae family. Its sesquiterpene lactones have demonstrated anti-tumor activity, and the Vernonia chemicals (vernoniosides) of the pith have proven effective against drug-resistant malarial parasites, which are very common within the range of this plant. Vernonia have been part of Tanzanian folk medicine for hundreds of years. The WaTongwe traditionally use Vernonia for stomachaches and several parasitic infections. V. latifolia has been reported to stop bleeding by inducing clot formation. The leaves are used in soup and stew as a strength-giving tonic by the local people after soaking them in water and cooking them. They also widely use Vernonia to treat parasites and other ailments in themselves and their livestock, indicating potential agricultural applications for other countries. Additionally, it is documented that Vernonia is used locally as an insecticide. Study has been conducted to evaluate the effect(s) of a novel water-soluble leaf extract of Vernonia amygdalina (VA) on human breast cancer cell DNA synthesis. MCF-7 cell line, considered a suitable model, was used in this study. Treatment of cells with physiologically relevant concentrations of water-soluble VA extract potently inhibited DNA synthesis in a concentration-dependent fashion both in the absence and presence of serum. The studies demonstrate anticancer activities of both crude and fractions of a water-soluble leaf extract of VA. Earlier investigators have shown that purified fractions of chloroform extract of VA elicited anticancer effects in human carcinoma of the nasopharynx. The process began with chloroform extraction of VA dried leaves to generate fractions A and B. Purification of A between 10% aqueous methanol and petroleum ether yielded an aqueous methanol fraction D. Fractionation of fraction D with silicic acid chromatography resulted in two cytotoxic fractions called F and H. Further chromatography of fraction H produced colorless oil called vernodaline, while rechromatography of the cytotoxic fraction F yielded two similar crystalline compounds, vernolide and vernomygdine. These three pure fractions elicited cytotoxic effects in human carcinoma nasopharynx cells with IC50 values of 1.8, 2.0, and 1.5 ug/ml respectively. The investigators concluded that the activities of these three compounds were dependent on their possessions of the or-methyl-7-lactone group as part of their structures. Jisakaand colleagues also showed that vernodaline and vernolide elicited antitumoral effects in leukemia cells P-388 and L-1210 with IC50 values of 0.11 and 0.17 ug/ml for vernodaline and 0.13 and 0.11 ng/ml for vernolide, respectively. Phytochemical analysis of V. amygdalina samples collected at Mahale from individual plants known to be used by chimpanzees revealed the presence of two major classes of bioactive compounds. A number of known sesquiterpene lactones, and 13 new stigmastane-type steroid glucosides and their freely occurring aglycones, have been isolated (Ohigashi et al. 1991, Jisaka et al. 1992a, 1992b, 1993a, 1993b). The sesquiterpene lactones present in V. amygdalina are also found in V. colorata and in a number of other Vernonia species. They are well known for their anthelmintic, antiamoebic, antitumor, and antibiotic properties (Toubiana and Gaudemer 1967, Kupchan et al. 1969, Asaka et al. 1977, Gasquet et al. 1985, Jisaka et al. 1992a, 1993b). Crude methanol extracts of the leaves exhibited immunosuppressive activity and inhibition of the process that initiates the first stage of tumor cell growth (Koshimizu et al. 1993). The cytotoxic sesquiterpene lactones were found to be most abundant in the leaves and bark. Vernonia leaves are thus used to treat stomachaches and parasitic infections, and the plant is also used as an insecticide, strength giver, and a blood clotter (McGraw Hill, 2000). Further, a traditional report from Indian traditional medicine has found that the tropical plant Vernonia anthelmintica seeds are both anti-inflammatory and cytotoxic. Alopecia is the absence or slowing of hair growth in an area of the body where hair formerly grew. It may be caused by physical damage to the hair itself or to the hair follicles, but it is most often the result of changes in the natural growth cycle of hair. In some types of alopecia, the growth cycle is disrupted by some temporary situation such as a chemical imbalance or stress. However, the vast majority (95%) of cases of hair loss in both men (male pattern baldness) and women (female diffuse baldness) are genetic in origin. Below the surface of the skin is the hair root, which is enclosed within a hair follicle. At the base of the hair follicle is the dermal papilla (or papilla). The dermal papilla is fed by the bloodstream which carries nourishment to produce new hair. The dermal papilla is a structure very important to hair growth because it contains receptors for male hormones and androgens. Androgens regulate hair growth and in scalp hair androgens may cause the hair follicle to get progressively smaller and contribute to the development of alopecia (Hoffmann, 2001). Causes of hair loss are varied. Six major types of hair loss are namely alopecia areata, androgenetic alopecia, anagen effluvium (cancer treatment hair loss), self induced hair loss, telogen effluvium and scarring alopecia. Other types of hair loss include syphilitic alopecia (usually a manifestation or secondary syphilis), scleroderma (a disease that causes fibrosis i.e. hardening and tightening of the skin which interferes with the normal functioning of the hair follicles and growth of the hair and tinea capitis (which causes hair loss by digesting the keratin of the hair). Alopecia areata is thought to be an auto-immune disease of the hair, initially appearing as a rounded bare patch about an inch across the sclap. Alopecia areata affects both men and women equally and is often experienced first in childhood. Androgenetic alopecia accounts for 95% of all hair loss. It can affect both men and women although men experience a much greater degree of loss. When androgenetic alopecia occurs, large active hair follicles in specific areas begin to change to smaller less active ones that shrink slightly with each new growth cycle. Testosterone 5a-reductase converts testosterone to 5a-DHT. 5a-DHT causes the hair shafts to narrow producing progressively finer hairs with each new growth cycle until eventually the hair becomes transparent and stop emerging. Thus this male hormone, 5a- DHT contributes to androgenetic alopecia in those who are genetically predisposed. It is interesting to note that individuals with a deficiency in testosterone 5a-reductase do not develop androgenetic alopecia. This is because the body is unable to convert testosterone into 5a-DHT (Hoffmann et al., 2000: Hibberts et al., 1998). Anagen Effluvium is the sudden hair loss which occurs as a result of chemicals or radiation, such as the hair loss that results during certain types of chemotherapy or radiation treatment. The hair loss is usually sudden occurring 1 to 3 weeks after expose to the chemicals or radiation has occurred. Damage to the hair in some cases is self inflicted sometimes consciously or unconsciously. The two main types of self induced hair loss are trichotillomania (which results from the continuous pulling or plucking of the hair) and traction alopecia (usually caused by continuous and excessive pulling on the hair due to various types of hairstyling). Telogen Effluvium occurs when sudden or severe stress causes an increase in the shedding of hair (Brajac et al., 2003). Scarring alopecia occurs when there is inflammation in the hair follicles due to infection. It is easy to identify a case of severe scarring alopecia because there will be rough patches on the surface of the scalp made up of small blood vessels and connective tissue. Scarring alopecia is mainly caused by Discoid Lupus Erythematosus, Lichen Planus, Pseudopelade of Brocq, Aplasia Cutis Congentia or Congenital Atrichia Several drugs are available to treat alopecia such as 5a-DHT inhibitors (Anti-androgens), SOD (Super oxide dismutases) mimetics, Vasodilators, Activation of PGHS-1 (Prostaglandin-H synthase-1) and Potassium channel openers (PCOs). The main cause of hair loss is the binding of 5a-DHT to the androgen receptors. The term "5