Many factors, including pathogens, environmental change and breeding techniques, affect honeybee immunity/resistance, so substances and natural supplements that enhance it are desired. To eliminate the impact of unknown external factors, in 2016 a cage experiment was conducted under constant laboratory conditions (35 °C, 65% relative humidity). Bees in the control group were fed with sugar dissolved in water at ratio 1:1 ad libitum with no additives, while the other group was fed with sugar syrup (1:1) supplemented with piperine (3 µg/ml) ad libitum. The piperine-treated workers lived 9 days longer compared to the control group. In the piperine-consuming group, protein concentration and the activities of antioxidative enzymes, such as superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) and glutathione S-transferase (GST), were higher than in the control group. The activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) were also higher in the piperine-treated group. Neutral and acidic proteases inhibitors, as well as neutral protease activities, were higher in the haemolymph of the piperine-treated workers than in untreated bees. Acidic protease activities in the haemolymph were higher in untreated workers only on days 18 and 32. Alkaline protease activities in the control bees were higher from day 10. From 10 days old, the total antioxidant capacity level was significantly higher in the haemolymph of piperine-treated workers. Piperine decreased DNA methylation levels significantly in the older bees. The compound could have the potential to be a natural diet supplement increasing apian resistance to stress factors.

Previous research has shown that resveratrol can increase cerebral blood flow (CBF) in the absence of improved cognitive performance in healthy, young human subjects during the performance of cognitively demanding tasks. This lack of cognitive effects may be due to low bioavailability and, in turn, reduced bioefficacy of resveratrol in vivo. Piperine can alter polyphenol pharmacokinetics, but previous studies have not investigated whether this affects the efficacy of the target compound. Therefore, the objective of the present study was to ascertain whether co-supplementation of piperine with resveratrol affects the bioavailability and efficacy of resveratrol with regard to cognition and CBF. The present study utilised a randomised, double-blind, placebo-controlled, within-subjects design, where twenty-three adults were given placebo, trans-resveratrol (250 mg) and trans-resveratrol with 20 mg piperine on separate days at least a week apart. After a 40 min rest/absorption period, the participants performed a selection of cognitive tasks and CBF was assessed throughout the period, in the frontal cortex, using near-IR spectroscopy. The presence of resveratrol and its conjugates in the plasma was confirmed by liquid chromatography–MS analysis carried out following the administration of the same doses in a separate cohort (n 6). The results indicated that when co-supplemented, piperine and resveratrol significantly augmented CBF during task performance in comparison with placebo and resveratrol alone. Cognitive function, mood and blood pressure were not affected. The plasma concentrations of resveratrol and its metabolites were not significantly different between the treatments, which indicates that co-supplementation of piperine with resveratrol enhances the bioefficacy of resveratrol with regard to CBF effects, but not cognitive performance, and does this without altering bioavailability.

Six amide alkaloids of Piper guineense were tested for antifeedant activity against fifth instar larvae of Chilo partellus in choice assays. These amides include piperine, Δα, β-dihydropiperine, wisanine, Δα, β-dihydrowisanine, trichostachine and N-isobutyl-trans-2-trans-4-eicosadienamide. Piperine and its dihydrosaturated derivative exhibited the most potentantifeedant activity. Δα, β-dihydrowisanine and trichostachine were intermediate in activity followed by wisanine. The N-isobutyl derivative was the least active. These results suggest that the presence of a methylenedioxybenzene and an alicyclic amide group in the compound may be crucial for high antifeedant activity.