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The purpose of this investigation was to determine ¹H-NMR profiling and antioxidant activity of the most common types of honey, namely, citrus honey (HC1) (Morcott tangerine L. and Jaffa orange L.), marjoram honey (HM1) (Origanum majorana L.), and clover honey (HT1) (Trifolium alexandrinum L.), compared to their secondary metabolites (HC2, HM2, HT2, respectively). By using a ¹H-NMR-based metabolomic technique, PCA, and PLS-DA multivariate analysis, we found that HC2, HM2, HC1, and HM1 were clustered together. However, HT1 and HT2 were quite far from these and each other. This indicated that HC1, HM1, HC2, and HM2 have similar chemical compositions, while HT1 and HT2 were unique in their chemical profiles. Antioxidation potentials were determined colorimetrically for scavenging activities against DPPH, ABTS, ORAC, 5-LOX, and metal chelating activity in all honey extract samples and their secondary metabolites. Our results revealed that HC2 and HM2 possessed more antioxidant activities than HT2 in vitro. HC2 demonstrated the highest antioxidant effect in all assays, followed by HM2 (DPPH assay: IC50 2.91, 10.7 μg/mL; ABTS assay: 431.2, 210.24 at 50 ug/mL Trolox equivalent; ORAC assay: 259.5, 234.8 at 50 ug/mL Trolox equivalent; 5-LOX screening assay/IC50: 2.293, 6.136 ug/mL; and metal chelating activity at 50 ug/mL: 73.34526%, 63.75881% inhibition). We suggest that the presence of some secondary metabolites in HC and HM, such as hesperetin, linalool, and caffeic acid, increased the antioxidant activity in citrus and marjoram compared to clover honey.

Data revealed that Egyptian clover were visited by 22 genus of arthropods belong to 16 families and 7 orders. The identified species were classified to phytophagous, Nectarivore, predatory insects. During both seasons Apis mellifera L. and Megachile sp. were the most abundant pollinators detected at the first week of May till the end of flowering season in mid-June. The highest activity period for A. mellifera was detected at 11:00 am. However, the lowest activity was found at 3:00 pm. and 5:00 pm. in both seasons, respectively, with insignificant difference between them in the first season. Whereas the highest activity period for Megachile sp. was detected at 1:00 pm. and the lowest activity was found at 7:00 am. During both seasons. The free pollination treatment produced the highest mean number of seeds per head followed by the caged with honeybees followed by the caged without honeybees treatment with average (48.15, 43.85 and 13.20 seeds /head) and (51.10, 46.10 and 10.85 seeds /head) during 2017 and 2018 seasons, respectively. The caged plants without honeybees produced the low weight of 1000 seed. Whereas the non-caged treatment produced the highest weights with an average (2.75 and 2.55 g) and (3.50 and 3.90 g) during both seasons, respectively.

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Background Honeybees provide a wealth of valuable natural products containing health-promoting bioactive compounds, including honey, bee bread, bee venom, bee pollen, propolis, and royal jelly. In the present study, we investigated the chemical composition of four honeybee products (bees, honey, royal jelly, and bee bread) derived from three medicinal plants (marjoram, trifolium, and citrus) using headspace GC-MS. Results GC-MS analysis coupled with the headspace method resulted in identification of 24 volatile compounds in marjoram honey, 14 volatile compounds in trifolium honey, and 25 volatile compounds in citrus honey, e.g., some of these compounds appeared in all three types of honey aroma, which are 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one, 2-furancarboxaldehyde, 5-(hydroxymethyl) and other unique compounds specific for each type where 23 compounds were from marjoram bees, 38 compounds from trifolium bees, and about 37 compounds were identified in citrus bees where 2,4-decadienal, (E, E) and methyl N-methyl anthranilate were common in all. Furthermore, the volatile compounds of all three types of royal jelly aroma were acetic acid, 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one, 8-nonen-2-one and furfural where one compound appeared in both marjoram and trifolium royal jelly that is 2-furancarboxaldehyde,5-(Hydroxymethyl) and the volatile compounds in marjoram and citrus are 2,3-butanediol and 5-methylfurfural also only one volatile compound appear in both trifolium and citrus royal jelly that is furfur alcohol, Finally, 3 compounds from marjoram bee bread, 30 volatile compounds from trifolium bee bread, and 3 volatile compounds in citrus bee bread were identified. Conclusions A detailed metabolomic analysis of the four honey product groups revealed an intriguing chemical diversity, with each sample exhibiting its own chemical fingerprint.