P. hysterophorus is a herb reaching about 1.0 m in height. Its stem is longitudinally grooved and bears green leaves. The leaves are irregularly dissected and pubescent. The flower heads are terminal or axillary. These white flower heads are usually 0.5 mm in diameter. The fruits are broadly obovoid in shape and have dark brown colour (Anonymous, 2001).

P. hysterophorus is used in treatment of ulcerated sores, wounds, fever, anaemia and heart troubles (Kalsi et al, 1995).

The plant is used as a tonic, febrifuge, emmenagouge and as an analgesic in neuralgia. A decoction of the root finds use in treatment of dysentery (Anonymous, 2001).

Two sesquiterpene lactones; hysterin and dihydroisoparthenin; have been isolated from plants growing in Argentina and Jamaica (Picman et al, 1982). Histamine (0.585 %) is present in the aerial parts of the plant (Kamal & Mathur, 1991). Syringaresinol has also been isolated from this weed (Das et al, 1999).

Three ambrosanolides; 8α-epoxymethylacrylyloxyparthenin, its 11α,13-dihydro derivative and 8α-epoxymethylacrylyloxyambrosin; have been isolated from chloroform extract of the aerial parts (Chhabra et al, 1999). A novel sesquiterpenoid, charminarone (the first seco-pseudoguaianolide) has been isolated from the whole plant (Venkataiah et al, 2003).

Parthenin, hexacosanol, myricyl alcohol, β-sitosterol, campesterol, stigmasterol, betulin, ursolic acid, β-D-glucoside of β-sitosterol and saponin have been isolated from leaves. The saponin on hydrolysis yields oleanolic acid and glucose. The aqueous extract contains free amino acids, glucose, galactose and potassium chloride (4.8%) (Gupta et al, 1977). Methoxypseudoguaianolides viz. 13-methoxydihydroambrosin, 13-methoxydihydroparthenin and 2β,13α-dimethoxydihydroparthenin have been isolated from leaves (Bhullar et al, 1997). The leaves also contain parthenin, caffeic, chlorogenic, p-hydroxybenzoic, p-anisic, vanilic, salicylic, gentisic, neo-chlorogenic and proto-catechuic acids (Anonymous, 2003).Leaves contain about 5% parthenin (Anonymous, 2003).

Methanolic extract of flowers contains several constituents such as 2β-hydroxycoronopilin, 8β-hydroxycoronopilin, 11-H,13-hydroxyparthenin, parthenin and coronopilin (Anonymous, 2003). Parthenin (up to 8 %) is present in capitulum (Anonymous, 2003). Four new pseudoguaianolides (hysterones A-D), parthenin, coronopilin, 2β-hydroxycoronopilin and tetraneurin-A have also been isolated from the flowers (Ramesh et al, 2003). A new highly oxygenated pseudoguaianolide (8-β-acetoxyhysterone C), parthenin, coronopilin and hysterone C have been isolated from the flowers (Das et al, 2005).

Histamine (0.35 %) is present in the roots of plant (Kamal & Mathur, 1991). The roots contain parthenin, caffeic, chlorogenic, p-hydroxybenzoic, p-anisic, vanilic, salicylic, gentisic, neo-chlorogenic and proto-catechuic acids (Anonymous, 2003).

Antiamoebic activity of parthenin from P. hysterophorus has been evaluated in vitro against axenic and polyxenic cultures of Entamoeba histolytica. Parthenin has been found to show acute toxicity to the cultured organisms. Parthenin has activity comparable to that of metronidazole. The findings of this study suggest that parthenin may be useful in experimental hepatic amoebiasis (Sharma & Bhutani, 1988).

Antitumor effects of methanolic flower extract of P. hysterophorus have been studied in mice bearing transplantable lymphocytic leukemia. Markers such as glutathione, cytochrome P-450, glutathione transferase and UDP-glucuronyl transferase in liver tissues show significant changes ultimately leading to slow development of tumors. The extract also results in increased survival of the leukemic mice (Mukherjee & Chatterjee, 1993).

Crude ethanolic extract of P. hysterophorus has been evaluated for in vivo and in vitro activities against Trypanosoma evansi. In vivo trial has revealed that the extract exerts antitrypanosomal effect at intraperitoneal doses of 100 and 300 mg/kg body weight. 1000 mg/kg dose has caused toxicity in the animals (Talakal et al, 1995).

Parthenin and some of its derivatives were evaluated for antimalarial activity against a multidrug resistant strain of Plasmodium falciparum. Parthenin and related compounds have significant antimalarial action (Anonymous, 2003).

Herbicidal activity of parthenin has been evaluated on Ageratum conyzoides (billgoat weed) grown under in vitro conditions. The germination of A. conyzoides is retarded suggesting that parthenin might find use as an herbicide (Batish et al, 1997). It is reported that parthenin hinders the growth of A. conyzoides by altering the contents of some macromolecules and the specific activities of some enzymes (Singh et al, 2002).

Parthenium extract exhibits significant antiviral action against potato virus Y. This virus extensively damages the chilli crops. Parthenin might find use as an effective agent against potato virus Y (Anonymous, 2003).

The aqueous extracts of shoots have been evaluated for antifungal activity against three fungi viz., Drechslera tetramera, Aspergillus niger and Phoma glomerata. Lower concentrations (10, 20 and 30% extract) exhibit antifungal activity whereas higher concentrations are devoid of any such activity. Hence, the lower concentrations of extracts might find use as antifungal agent (Bajwa & Khalid, 2003).

The cold and hot water leaf extracts have been evaluated against Pythium aphanidermatum wherein they show 50.5% and 48.3% inhibition respectively (Anonymous, 2003).

The germination of freshly harvested seeds can be effected by the exposure time of light. There is an increase in germination rate from 8% in the dark to 68% in light. It indicates that light plays a major role in growth of plant from seeds (Pandey & Palni, 2005).

Gall induction by Epiblema strenuana results in a range of morphological and physiological changes in Parthenium. These effects have been evaluated in the rosette (young), pre-flowering (mature), and flowering (old) stages. Gall induction reduces the leaf-water potential, especially in flowering stage plants. In young and mature stage plants, galling reduces photosynthetic rates considerably. It means that E. strenuana has the potential to regulate P. hysterophorus (Florentine et al, (2005). Epiblema strenuana Walker (Lepidoptera: Tortricidae) induced stem galls of Parthenium hysterophorus result in the stress metabolism in plant, implying that E. strenuana may find use as biological control agent. (Raman et al, 2006)

Parthenium hysterophorus L can be affected by cell-free culture filtrate of Phoma herbarum FGCC 75. P. herbarum shoot, detached leaf and seedling contain 3-nitrophthalic acid which acts as a phytotoxin against P. hysterophorus. This constituent has a potential to be developed as a chemical control tool for this weed (Vikrant et al, 2006).