Seasonality Affects the Phenolic Composition and Erythroprotective Activity of Ora-Pro-Nobis (Pereskia aculeata) Leaves

Ora-pro-nobis (OPN) is a food plant with polyphenol-rich leaves. However, the influence of seasonality on their quantitative phenolic composition and how it impacts their bioactivities is unknown. OPN leaves were harvested throughout 12 months, and their individual phenolic content, antioxidant activity, and erythroprotection were assessed. The highest total phenolic content was recorded in September (736 mg GAE/100 g), and the lowest in October (104 mg GAE/100 g). September also exhibited the highest rutin and protocatechuic, p-coumaric, and caffeic acids concentrations. Rutin was the major compound throughout the year. Protocatechuic acid contents were correlated with the air relative humidity, solar radiation incidence, and air temperature. June sample presented the best 2,2-diphenyl-1-picrylhydrazyl scavenging activity (227 mg AAE/100 g), while August was the most efficient sample to Fe²⁺-chelating (450 mg EDTAE/100 g), and September exhibited the highest ferric reducing antioxidant power (285 mg AAE/100 g). The December sample showed the greatest protection of erythrocytes against osmotic stress (48% haemolysis). Under oxidative conditions, November extract reduced the most lipoperoxidation and haemoglobin oxidation, and July was the most effective against haemolysis. Thus, seasonality appears to be a crucial factor in the biosynthesis of bioactive compounds in OPN leaves, which alters their biological properties but not their safety for consumption.