Stingless bee (Meliponini) honey has long been considered a high-value functional food, but the perceived therapeutic value has lacked attribution to specific bioactive components. Examination of honey from five different stingless bee species across Neotropical and Indo-Australian regions has enabled for the first time the identification of the unusual disaccharide trehalulose as a major component representing between 13 and 44 g per 100 g of each of these honeys. Trehalulose is an isomer of sucrose with an unusual α-(1 → 1) glucose-fructose glycosidic linkage and known acariogenic and low glycemic index properties. NMR and UPLC-MS/MS analysis unambiguously confirmed the identity of trehalulose isolated from stingless bee honeys sourced across three continents, from Tetragonula carbonaria and Tetragonula hockingsi species in Australia, from Geniotrigona thoracica and Heterotrigona itama in Malaysia and from Tetragonisca angustula in Brazil. The previously unrecognised abundance of trehalulose in stingless bee honeys is concrete evidence that supports some of the reported health attributes of this product. This is the first identification of trehalulose as a major component within a food commodity. This study allows the exploration of the expanded use of stingless bee honey in foods and identifies a bioactive marker for authentication of this honey in associated food standards.

Photosensitization is a novel environmentally friendly technology with promising applications in the food industry to extend food shelf life. In this study, the natural food dye curcumin, when combined with visible light (430 nm), was shown to be an effective photosensitizer against the common phytopathogenic fungi Botrytis cinerea (the cause of grey mould). Production of the associated phytotoxic metabolites botrydial and dihydrobotrydial was measured by our newly developed and validated HRAM UPLC-MS/MS method, and was also shown to be reduced by this treatment. With a light dose of 120 J/cm², the reduction in spore viability was directly proportional to curcumin concentrations, and the overall concentration of both botrydial and dihydrobotrydial also decreased with increasing curcumin concentration above 200 µM. With curcumin concentrations above 600 µM, the percentage reduction in fungal spores was close to 100%. When the dye concentration was increased to 800 µM, the spores were completely inactive and neither botrydial nor dihydrobotrydial could be detected. These results suggest that curcumin-mediated photosensitization is a potentially effective method to control B. cinerea spoilage, and also to reduce the formation of these phytotoxic botryane secondary metabolites.

Haemodorum coccineum, commonly known as scarlet bloodroot, is a plant native to New Guinea and the northern most parts of Australia. The highly coloured H. coccineum is used by communities in Larrakia country for dyeing garments and occasionally to treat snake bites. Previous studies into H. coccineum have focused on its taxonomic classification, with this being the first evaluation of the chemical composition of the plant. Haemodoraceae plants are reported to contain phenylphenalenones (PhPs), which are highly conjugated polycyclic oxygenated aromatic hydrocarbons. We report the characterisation of 20 compounds extracted from the rhizome of H. coccineum: four sugars and 16 compounds belonging to the PhP family. The compounds include five aglycones and seven glycosylated compounds, of which four contain malonate esters in their structures. Characterisation of these compounds was achieved through 1D and 2D NMR, MS analysis and comparison to the known phytochemistry of other species from the Haemodorum genus. Preliminary anti-microbial activity of the crude extract shows significant inhibition of the growth of both gram-positive and gram-negative bacteria, but no activity against Candida albicans.

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