No abstract

Hot water treatment (HT) has proved to alleviate chilling injury (CI) in bell pepper and other Solanaceae species, this has been associated with the presence of metabolites such as sugars and polyamines, which protect the plasmatic membrane. However, it is unknown if the phenolic compounds in bell pepper play a role in the CI tolerance induced by the application of a HT. The aim of this study was to identify the specific phenolics associated with induced CI tolerance in bell pepper by HT (53 °C, 1 to 3 min). Fruit treated for 1 min (HT‐1 min) exhibited CI tolerance (the lowest symptom development, electrolyte leakage, and vitamin C loss) and was the chosen treatment for further experiments. The phenolic composition was affected by HT‐1 min and CI. Phenolics presented a strong correlation with the antioxidant activity. In fruit with CI tolerance, the concentration of seven compounds was increased, being quercetin‐O‐rhamnoside‐O‐hexoside and chlorogenic acid the most remarkable. Quercetin‐3‐O‐rhamnoside was accumulated only in fruit with induced tolerance, meanwhile orientin was particularly sensitive to heat and cold exposure. Thus, HT‐1 min (53 °C, 1 min) is a useful technology to induce CI tolerance in bell pepper and such tolerance is associated with the phenolic composition that may reduce the prevalence of oxidative stress during the storage under CI conditions.Practical ApplicationPhenolics induced by CI and HT may be useful to detect early stages of heat and chilling injuries in bell pepper and prevent the negative effect of such stresses even before its harvest and during commercial storage. Additionally, the phenolics associated with CI tolerance may be used as markers in breeding programs to create new chilling resistant cultivars.

The application of technologies to reduce papaya (Carica papaya L.) anthracnose, a disease caused by the fungus Colletotrichum gloeosporioides, most of the time results in a loss of nutrients and other bioactive compounds. This study was performed to determine the effect of hot water (HW; 48°C/20 min), calcium chloride (Ca; 1%/20 min), and their combination (HW‐Ca) in bioactive compounds and antioxidant activity of papaya inoculated with Colletotrichum gloeosporioides stored during 20 days at 12°C. HW‐Ca treated fruits showed higher ascorbic acid, phenolics content, and antioxidant activity than untreated and HW and Ca treated fruit, which correlated with the contents of ascorbic acid, phenolics, and β‐cryptoxanthin. Also, HW‐Ca treatment resulted in fruits showing lower decay area, greater firmness and color retention. The results suggest that HW‐Ca treatment could be used to reach higher antioxidant activity values and to preserve the postharvest quality parameters, whereas the development of anthracnose symptoms was delayed. Practical applications Papaya infected by Colletotrichum gloeosporioides and treated with hot water (HW) in combination with calcium chloride (Ca) had a good firmness, color retention, and higher antioxidant activity and content of ascorbic acid and phenolics, while the development of anthracnose symptoms was delayed. In this sense, the proposed HW‐Ca treatment of papaya is a strategy to protect against Colletotrichum gloeosporioides and to obtain fruits with good quality, resulting in an interesting postharvest alternative to the application of fungicides.

No abstract

BACKGROUND: Colletotrichum gloeosporioides causes anthracnose in a large number of crops. Synthetic fungicides are employed to prevent this disease, even though their effectiveness and safety is questionable. Thus, effective and innocuous antifungal compounds are proposed as natural alternatives against anthracnose. The hexane fraction of Vitex mollis pulp (HF-VM) reduces anthracnose incidence in papaya fruit; however, the active compounds and antifungal mechanism of HF-VM are unknown. The aims of this study were to characterize the activity of HF-VM sub-fractions (sHF 1 -sHF 7 ) against a thiabendazole-resistant Colletotrichum gloeosporioides strain, identify the chemical components and investigate the mechanism of the most active sub-fraction. RESULTS: The sHF 3 showed the highest inhibitory activity against Colletotrichum gloeosporioides with a minimal inhibitory concentration (MIC) of 0.5 mg mL −1 , whereas thiabendazole (TBZ) had a MIC value higher than 2 mg mL −1 . The gas chromatography-mass spectrometry (GC-MS) analysis showed that the compounds in sHF 3 were methyl 4-decenoate, caprylic acid, and 24-methylencycloartanol. These compounds are rarely found in fruits and are reported for the first time on Vitex species. The purified 24-methylencycloartanol was inactive (MIC > 0.5 mg mL −1 ). In contrast, the commercial standard of caprylic acid presented an elevated activity (MIC = 0.125 mg mL −1 ), indicating that this compound is the main one responsible for the antifungal properties of sHF 3 . Furthermore, the sHF 3 inhibited the spore germination and induced membrane disruption in both the spore and mycelium of Colletotrichum gloeosporioides.CONCLUSION: Vitex mollis fruit is a novel source of antifungal caprylic acid that could be employed as a marker to prepare standardized extracts with antifungal properties.