Comparison of the Antioxidant Activity of Commercial Honeys, Before and After In-Vitro Digestion

Abstract

Honey is a rich source of antioxidant and antiseptic compounds including Maillard reaction products, vitamins, carotenoids and polyphenols. The objective of the present study was to determine the effect of digestion on the antioxidant activity of a range of honey samples including two economy brands (Tesco and Lidl), a premium Irish brand (Fainne Oir Fine Foods) and a New Zealand Manuka honey. Samples were subjected to an in-vitro digestion which simulates the human gastric and intestinal digestion system. The antioxidant activity of the honey samples before and after digestion was determined by measuring total phenol content (TPC), 2,2-diphenyl-2-picrylhydrazyl hydrate assay (DPPH) radical scavenging and ferric reducing antioxidant potential (FRAP). The ability of the samples to protect against H 2 O 2 -induced DNA damage in the Caco-2 cell line was measured by the Comet assay. The Manuka honey had the highest TPC and the Tesco honey had the highest FRAP and DPPH scavenging activity. TPC was not altered following digestion however there was a signifi cant decrease in the FRAP values for Manuka and Tesco honey and in the DPPH radical scavenging activity for all four of the samples. The Tesco and Manuka honeys demonstrated a signifi cant protective effect against H 2 O 2 -induced DNA damage in Caco-2 cells, following digestion. The premium brand honey samples did not demonstrate signifi cantly higher antioxidant activity in comparison with economy brand honey.

The Influence of In Vitro Gastrointestinal Digestion on the Anticancer Activity of Manuka Honey

“…As shown in the table, the TPC of MH was 1.27 mg GAEq/g honey, until it decreased about 6-fold in the DMH (0.203 mg GAEq/g honey). Similar results were found by O'Sullivan et al [16], who monitored how the total content of polyphenols in different types of commercial honey changed, finding that, of the four types observed, even if Manuka honey had greatest amount of phenolic compounds, after in vitro gastrointestinal, it lost the greatest amount of phenolic compounds. Regarding the effects of gastrointestinal digestion on honey, there are no further studies, but, in several other food matrices, a significative decrease in the phenolic compounds with respect to the undigested sample was noted.…”

“…The TAC in MH, evaluated with FRAP and TEAC, was 261.73 and 251.89 µmol TEq/100 g honey, respectively, and was lowered in the sample representing the bioaccessible intestinal fraction to values of 119.81 and 114.67, respectively. The DPPH test, as in the studies of O'Sullivan et al [16] and Seraglio et al [27], showed a greater decrease in the undigested and the digested sample, suggesting that it is more specific to phenolic compounds than the other two methods used. In fact, the TAC value obtained from the MH (86.479 µmol TEq/100 g honey) decreased by approximately seven times (11.8214 µmol TEq/100 g honey) in DMH as the trend ofTPC and TFC.…”

“…A clear decrease in TPC after gastrointestinal digestion was also observed in extracts of pomegranate [18], papaya, jackfruit [19], and in fresh persimmons [20]. However, there are some studies in which there are no clear differences between the TPC of the undigested and digested samples [16,21]. The decrease observed in the various studies, including this work, could be due to the fact that some phenolic compounds are more sensitive than others to pH changes, and moreover the type of food matrix could change their exposure to different conditions of acidity/basicity during gastro-intestinal digestion.…”

“…As shown in Figure 3a,b, cell viability was reduced in a dose-and time-dependent manner in cells treated with MH or DMH compared to the control (untreated cells). In colorectal adenocarcinoma cells, IC 50 values (concentration required for 50% inhibition of cell growth) of MH were 30.2 mg/mL at 24 h, 19.16 mg/mL at 48 h and 16.97 mg/mL at 72 h. mg/mL) [16]. Similar results were also found in the work of Ariza et al, in which the IC50 of the HepG2 (human liver carcinoma cells) of the digested samples of strawberries and achenes were lower than the respective raw fruits [36].…”

“…The values of IC 50 were as follows: 28.36 mg/mL at 24 h, 16.11 mg/mL at 48 h and 14.32 mg/mL at 72 h. As mentioned in the introduction, there are few works that evaluate the biological effect of digested honey compared to the corresponding raw honey. This was done only in the work of O'Sullivan et al, which evaluated the effect of four different types of commercial honey on Caco-2 cells (human epithelial colorectal adenocarcinoma cells), observing that the dose needed to inhibit 50% of cell growth was lower in digested samples (0.5-2 mg/mL) compared to the undigested sample (over 6 mg/mL) [16]. Similar results were also found in the work of Ariza et al, in which the IC 50 of the HepG2 (human liver carcinoma cells) of the digested samples of strawberries and achenes were lower than the respective raw fruits [36].…”