Immunocytochemical localization of short-chain family reductases involved in menthol biosynthesis in peppermint.

Biosynthesis of the p-menthane monoterpenes in peppermint occurs in the secretory cells of the peltate glandular trichomes and results in the accumulation of primarily menthone and menthol. cDNAs and recombinant enzymes are well characterized for eight of the nine enzymatic steps leading from the 5-carbon precursors to menthol, and subcellular localization of several key enzymes suggests a complex network of substrate and product movement is required during oil biosynthesis. In addition, studies concerning the regulation of oil biosynthesis have demonstrated a temporal partition of the pathway into an early, biosynthetic program that results in the accumulation of menthone and a later, oil maturation program that leads to menthone reduction and concomitant menthol accumulation. The menthone reductase responsible for the ultimate pathway reduction step, menthone-menthol reductase (MMR), has been characterized and found to share significant sequence similarity with its counterpart reductase, a menthone-neomenthol reductase, which catalyzes a minor enzymatic reaction associated with oil maturation. Further, the menthone reductases share significant sequence similarity with the temporally separate and mechanistically different isopiperitenone reductase (IPR). Here we present immunocytochemical localizations for these reductases using a polyclonal antibody raised against menthone-menthol reductase. The polyclonal antibody used for this study showed little specificity between these three reductases, but by using it for immunostaining of tissues of different ages we were able to provisionally separate staining of an early biosynthetic enzyme, IPR, found in young, immature leaves from that of the oil maturation enzyme, MMR, found in older, mature leaves. Both reductases were localized to the cytoplasm and nucleoplasm of the secretory cells of peltate glandular trichomes, and were absent from all other cell types examined.

Study of embryotoxicity of mentha piperita L. during organogenesis in balb/c mice / Estudio de la embriotoxicidad de mentha piperita L. durante la organogénesis en ratones balb/c

Mentha piperita (Labiatae), commonly known as peppermint is a native Iranian herb which is used in folk medicine for various purposes. This study was carried out to reveal the teratogenic effect of Mentha piperita on mice fetuses. In this experimental study, pregnant Balb/c mice divided to four groups. Case group received 600 (treatment I) and 1200 (treatment II) mg/kg/day the hydroalcoholic extract of Mentha piperita during 6-15 of gestational days and one control group received normal saline during GD6-GD15 by gavages and other control group did not receive any matter during 6-15 of gestational days. Mice sacrificed at GD18 and embryos were collected. Macroscopic observation was done by stereomicroscope. 20 fetuses of each group were stained by Alizarin red-S and Alcian blue staining method. The Mean weight of fetuses decreased in treatment groups rather than control (P<0.05) but CRL there was no significant difference between treatments and controls groups. In the treatment I (600 mg/kg/day) and treatment II (1200 mg/kg/day), normal saline and control group, no gross congenital malformations were observed in fetuses. Treated fetuses also had no delayed bone ossification as determined by Alizarin red-S and Alcian blue staining method. This study showed that the hydroalcoholic extract of Mentha piperita (600 and 1200 mg/kg/day) has no teratogenic effect in mice fetuses if used continuously during embryonic period.

Mentha piperita (Labiatae), comúnmente conocida como menta, es una hierba nativa de Irán, que se utiliza en la medicina tradicional para diversos fines. Este estudio fue realizado para descubrir el efecto teratogénico de la Mentha piperita en fetos de ratones. Los ratones Balb/c preñadas fueron divididas en cuatro grupos. Los grupos recibieron 600 (tratamiento I) y 1200 (tratamiento II) mg/kg/día del extracto hidroalcohólico de Mentha piperita durante los días 6-15 de gestación (DG), mientras que un grupo control recibió solución salina normal durante los DG 6-15 vía oral y otro grupo control sano no recibió substancia durante los DG 6-15. Los ratones fueron sacrificados el DG 18, recolectando los fetos. Se realizó la observación macroscópica mediante un estereomicroscopio. 20 fetos de cada grupo se tiñeron por el método de rojo de alizarina-S y azul de Alcián. La media de peso de los fetos disminuyó más en los grupos de tratamientos que los controles (p <0,05), pero CRL no presentó diferencias significativas entre los tratamientos y los grupos control. En los fetos del grupos tratamiento I (600 mg/kg/día), tratamiento II (1200 mg/kg/día), solución salina normal y control no se observó ninguna malformación congénita grave. Los fetos tratados tampoco tuvieron osificación ósea retrasada según lo determinado por el método de rojo de alizarina-S y azul de Alcián. Este estudio mostró que el extracto hidroalcohólico de Mentha piperita (600 y 1200 mg/kg/día) no tiene efectos teratogénicos en fetos de ratones al ser utilizado continuamente durante el período embrionario.

[Effect of enhanced UV-B radiation on photosynthetic structure and photosynthetic characteristics of Mentha piperita].

OBJECTIVE: To reveal the effects of UV-B radiation on the growth of medical plant Mentha piperita, simulate an enhanced UV-B radiation and evaluate intensity of radiation on the photosynthesis of M. piperita. METHOD: Three different levels of UV-B radiation were set in the experiment which included: natural light control (0 W x m(-2)), light UV-B radiation stress (0.15 W x m(-2)) and heavy UV-B radiation stress (0.35 W x m(-2)). The chloroplast ultrastructure, photosynthesis indexes and chlorophyll fluorescence parameters of the M. piperita were observed under the three treatments. RESULT: Although the chloroplast ultrastructure was destroyed to some degree under the light UV-B radiation stress, F(v)/(F)m, F(v)/F(o), qP, phiPS II and ETR could resume to the comparative level of natural light control. At the same time, qN increased firstly and decreased thereafter. But under the high strength UV-B radiation stress, the photosynthetic structures were badly destroyed, which could not recover through protecting mechanism by itself. CONCLUSION: It was showed that M. piperita was able to protect photosynthetic structures by increasing respiration and dissipation when photosynthetic capacity reduced under light UV-B radiation stress. It is demonstrated that M. piperita has high adaptation to light UV-B radiation stress, which is kind of promising medical plant for area with higher UV-B radiation.

Plasmolysis and recovery of different cell types in cryoprotected shoot tips of Mentha X piperita.

Successful cryopreservation of plant shoot tips is dependent upon effective desiccation through osmotic or physical processes. Microscopy techniques were used to determine the extent of cellular damage and plasmolysis that occurs in peppermint (Mentha x piperita) shoot tips during the process of cryopreservation, using the cryoprotectant plant vitrification solution 2 (PVS2) (30% glycerol, 15% dimethyl sulfoxide, 15% ethylene glycol, 0.4 M sucrose) prior to liquid-nitrogen exposure. The meristem cells were the smallest and least plasmolyzed cell type of the shoot tips, while the large, older leaf and lower cortex cells were the most damaged. When treated with cryoprotectant solutions, meristem cells exhibited concave plasmolysis, suggesting that this cell type has a highly viscous protoplasm, and protoplasts have many cell wall attachment sites. Shoot tip cells were most severely plasmolyzed after PVS2 treatment, liquid-nitrogen exposure, and warming in 1.2 M sucrose. Successful recovery may be dependent upon surviving the plasmolytic conditions induced by warming and diluting treated shoot tips in 1.2 M sucrose solutions. In peppermint shoot tips, clumps of young meristem or young leaf cells survive the cryopreservation process and regenerate plants containing many shoots. Cryoprotective treatments that favor survival of small, meristematic cells and young leaf cells are most likely to produce high survival rates after liquid-nitrogen exposure.