BackgroundVanilla planifolia is an important Orchid commercially cultivated for the production of natural vanilla flavour. Vanilla plants are conventionally propagated by stem cuttings and thus causing injury to the mother plants. Regeneration and in vitro mass multiplication are proposed as an alternative to minimize damage to mother plants. Because mass production of V. planifolia through indirect shoot differentiation from callus culture is rare and may be a successful use of in vitro techniques for producing somaclonal variants, we have established a novel protocol for the regeneration of vanilla plants and investigated the initial biochemical and molecular mechanisms that trigger shoot organogenesis from embryogenic/organogenic callus.ResultsFor embryogenic callus induction, seeds obtained from 7-month-old green pods of V. planifolia were inoculated on MS basal medium (BM) containing TDZ (0.5 mg l-1). Germination of unorganized mass callus such as protocorm -like structure (PLS) arising from each seed has been observed. The primary embryogenic calli have been formed after transferring on BM containing IAA (0.5 mg l-1) and TDZ (0.5 mg l-1). These calli were maintained by subculturing on BM containing IAA (0.5 mg l-1) and TDZ (0.3 mg l-1) during 6 months and formed embryogenic/organogenic calli. Histological analysis showed that shoot organogenesis was induced between 15 and 20 days after embryogenic/organogenic calli were transferred onto MS basal medium with NAA (0.5 mg l-1). By associating proteomics and metabolomics analyses, the biochemical and molecular markers responsible for shoot induction have been studied in 15-day-old calli at the stage where no differentiating part was visible on organogenic calli. Two-dimensional electrophoresis followed by matrix-assisted laser desorption ionization time-of-flight-tandem mass spectrometry (MALDI-TOF-TOF-MS) analysis revealed that 15 protein spots are significantly expressed (P < 0.05) at earlier stages of shoot differentiation. The majority of these proteins are involved in amino acid-protein metabolism and photosynthetic activity. In accordance with proteomic analysis, metabolic profiling using 1D and 2D NMR techniques showed the importance of numerous compounds related with sugar mobilization and nitrogen metabolism. NMR analysis techniques also allowed the identification of some secondary metabolites such as phenolic compounds whose accumulation was enhanced during shoot differentiation.ConclusionThe subculture of embryogenic/organogenic calli onto shoot differentiation medium triggers the stimulation of cell metabolism principally at three levels namely (i) initiation of photosynthesis, glycolysis and phenolic compounds synthesis; (ii) amino acid - protein synthesis, and protein stabilization; (iii) sugar degradation. These biochemical mechanisms associated with the initiation of shoot formation during protocorm - like body (PLB) organogenesis could be coordinated by the removal of TDZ in callus maintenance medium. These results might contribute to elucidate...

Abstract:The Mauritian population has a long tradition in the use of ethno-medicine, and the practice is still strong, especially in the treatment of minor ailments. Such interest stems from an existing culture, and many "tisanes" are still prepared from plant materials and sold in several markets around the island. This paper will focus on the various chemical/biological screening techniques currently being used to evaluate the biological properties of medicinal plant extracts. Particular emphasis will be put on extraction and various screening for biological/pharmacological properties. Due consideration will be given to the pharmacological approaches that utilize different animal models for the in vitro and in vivo screening of medicinal plant extracts.

Essential oils are among the secondary metabolites of higher plants. These fragrant compounds comprise volatile terpenes, sesquiterpenes as well as their derivatives. The antimicrobial attributes of essential oils have been recognized long ago but only recently it has been established scientifically. 1,2) Among the essential-oil bearing families are the Asteraceae (Compositae). This family is one of the largest plant family with over 1000 genera and 25000 species and growing in several different habitats. Many of the plants from this family are reputed to have medicinal properties and enter the local pharmacopeias of countries and for example, several Tagetes species have been found to possess anti-microbial activity.3,4) The anti-microbial activity of Tagetes minuta is well established against organisms such as Bacillus subtilis, Escherichia coli, Staphylococcus aureus, S. epididermis and Pseudomonas aerugunisa. This property has been ascribed to the presence of flavonoids in the leaf extract. 5)Several species of the genus Psiadia also belonging to the Asteraceae family are used in the traditional pharmacopoeia of Africa to treat several ailments such as abdominal pains and colds in the head, 6) as expectorant for bronchitis and asthma, 7) a poultice for rheumatoid arthritis, 8) and as a plaster cast for broken bones by the Bedouin. 9)In Mauritius, Psiadia species have been reported to be used medicinally. The species are: P. viscosa, P. terebinthina, P. arguta, P. lithospermifolia and P. penninervia. They are all known under one common vernacular name, which is "Baume de l'Ile Plate". In the local pharmacopeia, leaves of Psiadia plants are usually employed as poultice or in herbal teas to treat pulmonary infections and minor wounds and burns. 10) In the literature, there exists limited information on the essential oil composition of Psiadia species. P. arabica from Saudi Arabia has been reported to contain b-pinene as most abundant constituent (37%).11) Other components are present albeit as trace amounts. P. salviifolia has been reported to contain b-pinene, limonene, g-terpinene, p-cymene, a-copaene, linalool, b-bourbonene, a-himachalene, g-cadinene, d-cadinene, g-elemene and a hydroxy derivative of calarene while P. altissima contains sesquiterpenoids such as Tmuurolol and b-eudesmol (2.2%) and d-cadinol (1.2%). 12,13) The Psiadia species which grow on Mauritius have also been studied and the compositon of the leaf oil of three of them has already been reported in the literature.10,14,15) P. lithospermifolia has been reported to contain (E)-isoasarone as the major component (51.55%). P. viscosa has been reported to contain pentyl-4-(1-methylethyl benzoate) (25.86%), and (Z)-isoasarone (13.35%) as major components. The leaf oil of P. arguta, the most endangered species locally, is characterized by the presence of isoeugenol (56.5%) as the major component. 14,15) It can already be observed that the composition of the Psiadia species varies extensively. This may be attributed to several factors and one of the...

No abstract