UPLC-QTOF-MS analysis of cytotoxic and antibacterial extracts of Hechtia glomerata Zucc

Hechtia glomerata, a Mexican medicinal plant employed against bacterial infections and as food, is taxonomically related to the genus Tillandsia which has anticancer activity. Organic and aqueous extracts of H. glomerata leaves were prepared and tested for cytotoxic and antibacterial activity. UPLC-QTOF-MS analysis determined the chemical composition of active extracts to find cytotoxic and antibacterial compounds. Hexane extract was cytotoxic against HepG2, Hep3B and MCF7 (IC₅₀: 24-28 µg/mL), whereas CHCl₃/MeOH extract against PC3 and MCF7 (IC₅₀: 25 and 32 µg/mL). CHCl₃/MeOH extract showed antibacterial activity against Staphylococcus aureus and Enterococcus faecium (MIC: 125 and 62.5 µg/mL). Hexane extract cytotoxic compounds were β-sitosterol, stigmasterol, phytol and ursolic acid. CHCl₃/MeOH extract antibacterial and/or cytotoxic compounds were daucosterol, oleanolic acid, resveratrol, quercetin, kaempferol, apigenin, cyanidin, p-coumaric acid and caffeic acid. This plant could be useful against bacterial infections and cancer. However, in vivo studies are needed to determine its toxicity and therapeutic efficacy.

The occurrence of crassulacean acid metabolism in Cymbidium (Orchidaceae) and its ecological and evolutionary implications

Crassulacean acid metabolism (CAM) is one of the photosynthetic pathways regarded as adaptations to water stress in land plants. Little is known about correlations among the level of CAM activity, environment of habitat, life form, and phylogenetic relationship of a plant group from an evolutionary perspective. We examined these relationships in 18 species of Cymbidium (Orchidaceae) because the genus shows distinctive diversification of habitats and life forms. The photosynthetic type was classed into three categories, strong CAM, weak CAM, and C(3) on the basis of CAM activity. CAM expression in Cymbidium was confined to the epiphytic and lithophytic species. Especially, all of these species from tropical to subtropical rainforest exhibited CAM activity. On the other hand, the terrestrial species always exhibited C(3) metabolism irrespective of their varied habitats. Regarding the evolution of photosynthetic characters, weak CAM was the ancestral state in Cymbidium and strong CAM and C(3) metabolism occurred subsequently. The evolution of strong CAM likely enabled Cymbidium to extend to exposed sites in tropical lowland where marked water stress exists. Further, different levels of CAM activity characterized each species and such potential plasticity of CAM may realize the radiation of Cymbidium into sites with different environmental conditions.

Multiple origins of crassulacean acid metabolism and the epiphytic habit in the Neotropical family Bromeliaceae

The large Neotropical family Bromeliaceae presents an outstanding example of adaptive radiation in plants, containing a wide range of terrestrial and epiphytic life-forms occupying many distinct habitats. Diversification in bromeliads has been linked to several key innovations, including water- and nutrient-impounding phytotelmata, absorptive epidermal trichomes, and the water-conserving mode of photosynthesis known as crassulacean acid metabolism (CAM). To clarify the origins of CAM and the epiphytic habit, we conducted a phylogenetic analysis of nucleotide sequences for 51 bromeliad taxa by using the plastid loci matK and the rps16 intron, combined with a survey of photosynthetic pathway determined by carbon-isotope ratios for 1,873 species representing 65% of the family. Optimization of character-states onto the strict consensus tree indicated that the last common ancestor of Bromeliaceae was a terrestrial C(3) mesophyte, probably adapted to moist, exposed, nutrient-poor habitats. Both CAM photosynthesis and the epiphytic habit evolved a minimum of three times in the family, most likely in response to geological and climatic changes in the late Tertiary. The great majority of epiphytic forms are now found in two lineages: in subfamily Tillandsioideae, in which C(3) photosynthesis was the ancestral state and CAM developed later in the most extreme epiphytes, and in subfamily Bromelioideae, in which CAM photosynthesis predated the appearance of epiphytism. Subsequent radiation of the bromelioid line into less xeric habitats has led to reversion to C(3) photosynthesis in some taxa, showing that both gain and loss of CAM have occurred in the complex evolutionary history of this family.