Bioactivity of the Genus Turnera: A Review of the Last 10 Years.

Turnera is a genus of plants whose biological activity has been widely studied. The importance of this genus, particularly Turnera diffusa, as a source of treatment for various conditions is evidenced by the large number of new studies that have evaluated its biological activity. Accordingly, the objective of this review was to compile the information published in the last ten years concerning the biological activities reported for Turnera spp. The present work includes 92 publications that evaluate 29 bioactivities and toxicological and genotoxic information on five species of this genus. Among the pharmacological effects reported, the antioxidant, hepatoprotective, neuroprotective, hypoglycemic, and aphrodisiac activities seem more promising. Phytochemicals and standardized plant extracts could offer alternative therapeutic remedies for various diseases. Although several flavonoids, cyanogenic glycosides, monoterpenoids, triterpenoids, and fatty acids have been isolated for Turnera plants, future research should focus on the identification of the main active principles responsible for these pharmacological activities, as well as to perform clinical trials to support the laboratory results.

Two Ways to Achieve the Same Goal-Two Validated Quantitative NMR Strategies for a Low-Abundance Natural Product in Standardized Extracts: The Case of Hepatodamianol in Turnera diffusa.

The quantification of low-abundance secondary metabolites in plant extracts is an analytical problem that can be addressed by different analytical platforms, the most common being those based on chromatographic methods coupled to a high-sensitivity detection system. However, in recent years nuclear magnetic resonance (NMR) has become an analytical tool of primary choice for this type of problem because of its reliability, inherent simplicity in sample preparation, reduced analysis time, and low solvent consumption. The versatility of strategies based on quantitative NMR (qNMR), such as internal and external standards and electronic references, among others, and the need to develop validated analytical methods make it essential to compare procedures that must rigorously satisfy the analytical well-established acceptance criteria for method validation. In this work, two qNMR methods were developed for the quantification of hepatodamianol, a bioactive component of T. diffusa. The first method was based on a conventional external standard calibration, and the second one was based on the pulse length-based concentration determination (PULCON) method using the ERETIC2 module as a quantitation tool available in TopSpin software. The results show that both procedures allow the content of the analyte of interest in a complex matrix to be determined in a satisfactory way, under strict analytical criteria. In addition, ERETIC2 offers additional advantages such as a reduction in experimental time, reagent consumption, and waste generated.

In vitro stimulation with radiofrequency currents promotes proliferation and migration in human keratinocytes and fibroblasts.

Capacitive-resistive electric transfer (CRET) therapies have been proposed as strategies for regeneration of cutaneous tissue lesions. Previous studies by our group have shown that intermittent stimulation with 448 kHz CRET currents at subthermal densities promotes in vitro proliferation of human stem cells involved in tissue regeneration. The present study investigates the effects of the in vitro exposure to these radiofrequency (RF) currents on the proliferation and migration of keratinocytes and fibroblasts, the main cell types involved in skin regeneration. The effects of the electric stimulation on cell proliferation and migration were studied through XTT and wound closure assays, respectively. The CRET effects on the expression and location of proteins involved in proliferation and migration were assessed by immunoblot and immunofluorescence. The obtained results reveal that electrostimulation promotes proliferation and/or migration in keratinocytes and fibroblasts. These effects would be mediated by changes observed in the expression and location of intercellular adhesion proteins such as ß-catenin and E-cadherin, of proteins involved in cell-to-substrate adhesion such as vinculin, p-FAK and the metalloproteinase MMP-9, and of other proteins that control both processes: MAP kinases p-p38, p-JUNK and p-ERK1/2. These responses could represent a mechanism underlying the promotion of normotrophic wound regeneration induced by CRET. Indeed, electric stimulation would favor completion of granulation tissue formation prior to the closure of the outer tissue layers, thus preventing abnormal wound cicatrization or chronification.

Acute Hypoglycemic and Antidiabetic Effect of Teuhetenone A Isolated from Turnera diffusa.

Diabetes mellitus is a chronic degenerative disease that causes long-term complications and represents a serious public health problem. Turnera diffusa (damiana) is a shrub that grows throughout Mexico and is traditionally used for many illnesses including diabetes. Although a large number of plant metabolites are known, there are no reports indicating which of these are responsible for this activity, and this identification was the objective of the present work. Through bioassay-guided fractionation of a methanolic extract obtained from the aerial part of T. diffusa, teuhetenone A was isolated and identified as the main metabolite responsible for the plant's hypoglycemic activity. Alpha-glucosidase inhibitory activity and cytotoxicity of this metabolite were determined. Hypoglycemic and antidiabetic activities were evaluated in a murine model of diabetes in vivo, by monitoring glucose levels for six hours and comparing them with levels after administering various controls. Teuhetenone A was not cytotoxic at the tested concentrations, and did not show inhibitory activity in the glucosidase test, and the in vivo assays showed a gradual reduction in glucose levels in normoglycemic and diabetic mice. Considering these results, we suggest that teuhetenone A has potential as an antidiabetic compound, which could be further submitted to preclinical assays.