Classification of Southeast Asian mints (Mentha spp.) based on simple sequence repeat markers.

Mentha is a complex genus encompassing many species as a consequence of their interspecific hybridization and polyploidy. Southeast Asian mints have been poorly distinguished though they are widely used for culinary and medical purposes. In this study, we have analyzed Southeast Asian mints and known varieties as well as a related Lamiaceae species (Nepeta sp.) using simple sequence repeat (SSR) markers and leaf morphology. Two types of mints were clearly distinguished based on their venation pattern and leaf shape index. We developed 12 SSR markers that allowed good amplification in the Mentha and another Lamiaceae species. In the SSR-based phylogram, the Mentha lines could be delimited into groups I-VI. The Southeast Asian mints divided into groups I and II, and the phylogram separated most of the available species, with groups I and II containing the known species M. × cordifolia and M. arvensis, respectively. The separation of the two groups was supported by a population structure analysis. The SSR markers developed in this study enabled the simultaneous classification of mints and will help improve our understanding of the genetic composition of known mint varieties and as yet unclassified Southeast Asian mints.

Synergistic effect of vacuum packaging and cold shock reduce lignification of asparagus.

This study was carried out to investigate the combined effects of vacuum packaging (VP) and cold shock (CS) of asparagus on lignification during storage at 4°C. Physiological and biochemical changes were analyzed. The VP + CS treatment reduced fresh weight loss and color change and prevented the increment of spear toughness the most compared to VP, CS, and control. Also, the VP + CS was most effective in suppressing the activities of lignin biosynthesis enzymes, including phenylalanine ammonia-lyase, cinnamyl-alcohol dehydrogenase, and peroxidase, thereby delaying lignin formation. In addition, the combined treatment delayed ethylene production peak and the reduction of total phenolic content. These results suggest that VP + CS may maintain eating quality of asparagus spears through delay of lignification. PRACTICAL APPLICATIONS: This study mainly focused on reducing lignification of asparagus spears using VP + CS, which is safe, eco-friendly, affordable, and practical. Our results showed that VP + CS significantly delayed lignification. Thus, VP + CS represents a promising postharvest handling approach for reducing the lignin content of asparagus, to preserve its integrity, and improve stability during shipment. This prospective technique will eliminate the use of chemical alternatives to prolong the storage life and maintain the quality of spears.

Investigation on the Epoxidation of Piperitenone, and Structure-activity Relationships of Piperitenone Oxide for Differentiation-inducing Activity.

Piperitenone oxide, a major chemical constituent of the essential oil of spearmint, Mentha spicata, induces differentiation in human colon cancer RCM-1 cells. In this study, piperitenone oxide and trans-piperitenone dioxide were prepared as racemic forms by epoxidation of piperitenone. The relative configuration between two epoxides in piperitenone dioxide was determined to be trans by 1H NMR analysis and nuclear Overhauser effect spectroscopy (NOESY) in conjunction with density functional theory (DFT) calculations. Optical resolution of (±)-piperitenone oxide by high-performance liquid chromatography (HPLC) using a chiral stationary phase (CSP) afforded both enantiomers with over 98% enantiomeric excess (ee). Evaluation of the differentiation-inducing activity of the synthetic compounds revealed that the epoxide at C-1 and C-6 in piperitenone oxide is important for the activity, and (+)-piperitenone oxide has stronger activity than (-)-piperitenone oxide. The results obtained in this study provide new information on the application of piperitenone oxide and spearmint for differentiation-inducing therapy. Furthermore, natural piperitenone oxide was isolated from M. spicata. The enantiomeric excess of the isolated natural piperitenone oxide was 66% ee. Epoxidation of piperitenone with hydrogen peroxide proceeded in a phosphate buffer under weak basic conditions to give (±)-piperitenone oxide. These results suggest that the nonenzymatic epoxidation of piperitenone, which causes a decrease in the enantiomeric excess of natural piperitenone oxide, is accompanied by an enzymatic epoxidation in the biosynthesis of piperitenone oxide.

Efficiency of salicylic acid or methyl jasmonate immersions on internal browning alleviation and physicochemical quality of Queen pineapple cv. "Sawi" fruit during cold storage.

The pineapples were dipped in salicylic acid (SA) (2.5 or 5.0 mM) or methyl jasmonate (MeJA) (0.01 or 0.1 mM) for 1, 2, or 3 hr and then held at 13 ± 1°C for 10 days. The parameters were determined after left the fruits at 25°C for 2 days. It was found that, in the tissue adjacent to the core, 5.0 mM SA for 2 hr and 0.01 mM MeJA for 3 hr alleviated chilling injury (CI) and maintained color than other treatments. The MeJA immersions lowered CI score, electrolyte leakage, and malondialdehyde content greater than other treatments. SA and MeJA immersions retarded polyphenol oxidase activity, total phenols, and induced antioxidant activity during storage. In the pulp tissue, SA treatment increased ascorbic acid and total sugar contents, and MeJA immersions enhanced bioactive compound and antioxidant enzyme activities than SA immersion. Therefore, MeJA immersions could alleviate CI and enhance antioxidant better than other treatments of pineapples during cold storage. PRACTICAL APPLICATIONS: Postharvest immersion at the optimum concentration of SA or MeJA can be applied for commercial scale in order to alleviate chilling of "Sawi" pineapple fruit during storage. MeJA treatment enhances antioxidant activity and reduces internal browning better than SA treatment in pineapple.

Physicochemical changes of 'Phulae' pineapple fruit treated with short-term anoxia during ambient storage.

The effects of short-term anoxia exposure for 16h on physicochemical changes of 'Phulae' pineapple fruit stored at ambient temperature (25±2°C) were investigated. The respiratory rate of the fruit was induced by the anoxia treatment. However, it retarded the increase in moisture loss and maintained both flesh and pulp colour by inhibiting polyphenol oxidase (PPO) activity of the both tissues. The anoxia exposure delayed the increase in total sugar content and enhanced total ascorbic acid content during storage. The half-cut pineapple fruit showed that the anoxia exposure completely inhibited internal transparency of the flesh tissue adjacent to core during the storage. In conclusion, the short-term anoxia exposure for 16h maintained postharvest quality, retarded physiological disorder and enhanced nutritional values of the pineapple fruit stored at ambient temperature (25±2°C).