Correlation Between Polyphenol Oxidase (PPO) Activity and Total Phenolic Contents in Crocus sativus L. Corms During Dormancy and Sprouting Stages

Growth and Biochemical Responses of Potato Cultivars under In Vitro Lithium Chloride and Mannitol Simulated Salinity and Drought Stress

Globally, drought and salinity stress critically constrain potato (Solanum tuberosum L.) production. Considering the impact of these stresses on crops and increasing food demand, insight into both tolerance and susceptibility is essential. The present study screens two potato cultivars, BARI-401 and Spunta, for their tolerance to simulated salinity and drought by in vitro LiCl and mannitol exposure. Plantlets treated with a range of LiCl (0, 10, 30, and 40 mM) and mannitol (0, 50, 100, 200, and 250 mM) concentrations were biochemically and physiologically characterized to assess their tolerance capacity. Shoot number, shoot length, root number, and root length were affected in both cultivars under higher LiCl and mannitol concentrations, even though Spunta was able to better maintain a higher shoot length under the 40 mM of LiCl and 250 mM of mannitol compared to BARI-401. The total phenol contents (TPC) in both cultivars were increased at the highest treatment concentration and the total flavonoids content (TFC) was decreased in BARI-401 as compared to Spunta. Higher free radical scavenging capacity (FRSC, low IC50 value) was recorded in Spunta as compared to BARI-401 with increasing treatment concentrations, which supports the high antioxidant capacity of Spunta. An inverse correlation between polyphenol oxidase (PPO) and TPC was noted in both cultivars. Peroxidase dismutase (POD) activity was increased significantly in both cultivars for all treatments, but activity was highest overall in Spunta. These physiological and biochemical analyses of both cultivars suggest that cultivar Spunta is more tolerant to salinity and drought stress. Further open-field experiments are required to confirm these results.

Biogenic copper nanoparticles from Avicennia marina leaves: Impact on seed germination, detoxification enzymes, chlorophyll content and uptake by wheat seedlings

Biogenic copper nanoparticles (Cu NPs) were synthesized using the aqueous crude extract of mangrove leaves, Avicennia marina (CE). GC-MS metabolite profiling of CE showed that their carbohydrates are mainly composed of D-mannose (29.21%), D-fructose, (18.51%), L-sorbose (12.91%), D-galactose (5.47%) and D-Talose (5.21%). Ultra-fine nanoparticles of 11.60 ±4.65 nm comprising Cu2O and Cu(OH)2 species were obtained with a carbohydrate and phenolic content of 35.6±3.2% and 3.13±0.05 mgGA/g, respectively. The impact of the biogenic Cu NPs on wheat seedling growth was dose-dependent. Upon treatment with 0.06 mg/mL of Cu NPs, the growth was promoted by 172.78 ± 23.11 and 215.94 ± 37.76% for wheat root and shoot, respectively. However, the lowest relative growth % of 81.94 ± 11.70 and 72.46 ± 18.78% were recorded for wheat root and shoot, respectively when applying 0.43 mg/mL of Cu NPs. At this concentration, peroxidase activity (POX) of the germinated wheat seeds also decreased, while ascorbic acid oxidase (AAO) and polyphenol oxidase (PPO) activities increased. Higher uptake of copper was observed in the root relative to the shoot implying the accumulation of the nanoparticles in the former. The uptake was also higher than that of the commercial Cu NPs, which showed an insignificant effect on the seedling growth. By treating the wheat leaves in foliar application with 0.06 mg/mL of Cu NPs, their contents of Chlorophyll a, Chlorophyll b, and total chlorophyll were enhanced after 21 days of application. Meanwhile, the high concentration (0.43 mg/mL) of Cu NPs was the most effective in reducing the leaf content of chlorophyll (a, b, and total) after the same time of application. The findings of this study manifest the potential of utilizing controlled doses of the prepared biogenic Cu NPs for inhibition or stimulation of seedling growth.

The Influence of Supercritical Carbon Dioxide on Graham Flour Enzyme Polyphenol Oxidase Activity

Graham flour is a form of whole wheat flour made by grinding the endosperm and is thus also the most nutritious. Generally, the enzyme polyphenol oxidase (PPO) catalyzes two different reactions in the presence of molecular oxygen: the hydroxylation of monophenols to ortho-diphenol and the oxidation of o-diphenol to o-quinone. The purpose of the work was to inactivate PPO activity to extend the shelf life of graham flour and at the same time preserve all the of its high-quality properties. The influence of supercritical CO₂ (scCO₂) treatment on PPO activity in graham flour was investigated. First, graham flour was exposed to scCO₂ conditions, then the proteins were extracted, and in the last step the concentration of total proteins and the specific activity of the PPO enzyme were determined by spectrophotometric assay. PPO activity decreased with an increase in treatment pressure. Furthermore, the flour quality characteristics that meet all needs for wheat end-use products after scCO₂ treatment have been preserved. No major changes in the structure of the granulate or shape of the flour particles were observed. A slightly reduced value of the moisture content in scCO₂-treated graham flour also implies an extension of the shelf life.

Quality enhancement of Dendrobium officinale and banana juice through probiotic fermentation using beneficial lactic acid-producing bacteria

Consumption of functional juice is becoming increasingly popular. This study aimed to evaluate the effect of probiotic fermentation with Bacillus sp. DU-106; Lactobacillus planturum Lp-43 and Lactobacillus rhamnosus Lr-156 on the biochemical and functional characteristics, antioxidant activities and storage stability of Dendrobium officinale and banana (DOB) juice. The cell levels of the lactic acid bacteria reached near 9 log copies/mL after fermentation at 32 °C for 36 h and could keep in this level after storage at 4 °C for 28 days. After fermentation, total acidity, flavonoids and polysaccharide contents of DOB juice increased, while pH, dissolved oxygen, nitrite, nitrate, vitamin C, β-carotene, sugar contents and antioxidant capacity slightly decreased. Compared with nonfermented DOB juice, polyphenol oxidase (PPO) and peroxidase (POD) activities of fermented DOB decreased significantly, but the color value and the content of total phenols and vitamin C decreased slightly in fermented DOB juice during storage. Overall, the probiotic fermentation with selected strains could improve the quality the DOB juice, enhance antioxidant capacity and storage stability, and destroy accumulation of nitrite and nitrate during storage. Findings of this study would help in the development of beneficial beverages in industrial production.