First insights into the diversity and functional properties of chitinases of the latex of Calotropis procera.

Chitinases (EC 3.2.1.14) found in the latex of Calotropis procera (Ait) R. Br. were studied. The proteins were homogeneously obtained after two ion exchange chromatography steps. Most proteins were identified individually in 15 spots on 2-D gel electrophoresis with isoelectric points ranging from 4.6 to 6.0 and molecular masses extending from 27 to 30 kDa. Additionally, 66 kDa proteins were identified as chitinases in SDS-PAGE. Their identities were further confirmed by mass spectrometry (MS) analysis of the tryptic digests of each spot and MS analysis of the non-digested proteins. Positive reaction for Schiff's reagent suggested the proteins are glycosylated. The chitinases exhibited high catalytic activity toward to colloidal chitin at pH 5.0, and this activity underwent decay in the presence of increasing amounts of reducing agent dithiothreitol. Spore germination and hyphae growth of two phytopathogenic fungi were inhibited only marginally by the chitinases but were affected differently. This suggested a complex relationship might exist between the specificity of the proteins toward the fungal species. The chitinases showed potent insecticidal activity against the Bruchidae Callosobruchus maculatus, drastically reducing survival, larval weight and adult emergence. It is concluded that closely related chitinases are present in the latex of C. procera, and the first experimental evidence suggests these proteins are involved more efficiently in defence strategies against insects rather than fungi.

Water relations and photosynthetic capacity of two species of Calotropis in a tropical semi-arid ecosystem.

BACKGROUND AND AIMS: Calotropis procera and Calotropis gigantea, originally from warm parts of Africa and Asia, are now pan-tropical and in ecological terms considered an indicator of overgrazed, disturbed lands; they grow successfully in dry areas. Variations in water relations, morphology and photosynthesis of the two species growing in the same habitat were studied to assess possible mechanisms of tolerance to drought and how these relate to their ecophysiological success. Also the hypothesis that their photosynthetic rate (A) under drought would be affected by stomatal and non-stomatal limitations was tested. METHODS: Water relations, gas exchange, water use efficiency (WUE), fluorescence parameters, pubescence and specific leaf area (SLA) of Calotropis procera and C. gigantea plants growing in the field were evaluated during the wet (WS) and dry (DS) seasons. RESULTS: The xylem water potential (ψ) was similar in both species during the WS and DS; drought caused a 28 % decrease of ψ. In C. procera, A, stomatal conductance (g(s)) and carboxylation efficiency (CE) were higher in the WS with half the values of those during the DS, this species being more affected by drought than C. gigantea. A high δ(13)C of C. gigantea (-26·2 ‰) in the WS indicated a higher integrated WUE, in agreement with its lower g(s). Leaves of C. gigantea were more pubescent than C. procera. Relative stomatal and non-stomatal limitation of A increased with drought in both species; no changes in maximum quantum yield of photosystem II (PSII; F(v)/F(m)) were observed. The decrease in the relative quantum yield of PSII (ϕ(PSII)) and in the photochemical quenching coefficient (q(P)) was more pronounced in C. procera than in C. gigantea. CONCLUSIONS: The photosynthetic capacity of C. procera was higher than that of C. gigantea. During the DS, A was regulated by stomatal and non-stomatal factors in a coordinated manner and drought did not cause chronic photoinhibition. A higher density of trichomes and leaf angle in C. gigantea may contribute to the maintenance of A and confer more efficient protection of photochemical activity in the DS. Ecophysiological traits such as high photosynthetic rate throughout the year even during the DS, and high WUE, highly pubescent leaves and low SLA observed in both species contribute to the establishment and growth of Calotropis in dry conditions.

Ultrastructural observations reveal the presence of channels between cork cells.

The ultrastructure of phellem cells of Quercus suber L. (cork oak) and Calotropis procera (Ait) R. Br. were analyzed using electron transmission microscopy to determine the presence or absence of plasmodesmata (PD). Different types of Q. suber cork samples were studied: one year shoots; virgin cork (first periderm), reproduction cork (traumatic periderm), and wet cork. The channel structures of PD were found in all the samples crossing adjacent cell walls through the suberin layer of the secondary wall. Calotropis phellem also showed PD crossing the cell walls of adjacent cells but in fewer numbers compared to Q. suber. In one year stems of cork oak, it was possible to follow the physiologically active PD with ribosomic accumulation next to the aperture of the channel seen in the phellogen cells to the completely obstructed channels in the dead cells that characterize the phellem tissue.

UNBS1450 from Calotropis procera as a regulator of signaling pathways involved in proliferation and cell death.

Despite significant progress in oncology therapeutics in the last decades, the urge to discover and to develop new, alternative or synergistic anti-cancer agents still remains. For centuries it has been known that the coarse shrub Calotropis procera is a very promising source of ascaricidal, schizonticidal, anti-bacterial, anthelmintic, insecticidal, anti-inflammatory, anti-diarrhoeal, larvicidal and cytotoxic chemicals. Different compounds like norditerpenic esters, organic carbonates, the cysteine protease procerain, alkaloids, flavonoids, sterols as well as numerous types of cardenolides have provided this plant for centuries with scientists' interest. The chemical class of cardenolides and their related bioactivity evaluation and structure-activity relationship (SAR) studies pointed out their therapeutic utility and led to the discovery of promising drug candidates. Recently the cardiotonic steroid UNBS1450 01 (derived from 2-oxovoruscharin 02) from C. procera was shown to additionally exert an anti-cancer activity. UNBS1450 01 has been proven to be a potent sodium pump inhibitor, showing anti-proliferative and cell death-inducing activities. This anti-cancer potential of UNBS1450 01 is achieved by disorganization of the actin cytoskeleton after binding to the sodium pump at the cellular membrane, by inducing autophagy-related cell death, by repressing NF-kappaB activation as well as by down-regulating c-Myc in cancer cells. We aim to review pharmacologically important chemical extracts from C. procera and focus more specifically on the anti-cancer activities of UNBS1450 01.