In honeybees there are three alleles of cytosolic malate dehydrogenase gene: F, M and S. Allele frequencies are correlated with environmental temperature, suggesting that the alleles have temperature-dependent fitness benefits. We determined the enzyme activity of each allele across a range of temperatures in vitro. The F and S alleles have higher activity and are less sensitive to high temperatures than the M allele, which loses activity after incubation at temperatures found in the thorax of foraging bees in hot climates. Next, we predicted the protein structure of each allele and used molecular dynamics simulations to investigate their molecular flexibility. The M allozyme is more flexible than the S and F allozymes at 50°C, suggesting a plausible explanation for its loss of activity at high temperatures, and has the greatest structural flexibility at 15°C, suggesting that it can retain some enzyme activity at cooler temperatures. MM bees recovered from 2 h of cold narcosis significantly better than all other genotypes. Combined, these results explain clinal variation in malate dehydrogenase allele frequencies in the honeybee at the molecular level.
Propolis is one of the economic bee products with biological activities, but these activities can vary according to the local plants and bee species. This study aimed to evaluate the cytotoxic and antityrosinase activity of the methanol-, hexane-, and dichloromethane-partitioned propolis extracts (MPE, HPE, and DPE, respectively) of two dominant stingless bee species in Thailand (Tetragonula laeviceps and Tetragonula pegdeni) sourced from four locations in Ratchaburi province and one location in Chiangmai province. Their antiproliferative/cytotoxic activity, as the relative cell viability, was screened against the liver (Hep-G2) and gastric carcinoma (KATO-III) cancer cell lines in comparison to the untransformed lung fibroblast (WI-38) cell line using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Interestingly, DPE7 was the extract that showed great potential anticancer properties because it was significantly higher cytotoxic to cancer cell lines (Hep-G2 and KATO-III, with IC50 values of 36.40 and 35.15 mg/mL, respectively) than to normal cell lines (WI-38, with IC50 values of 46.52 mg/mL). Although DPE7 did not exhibit the highest antityrosinase activity, its moderate antityrosinase activity (IC50 of 1.388 mg/mL) considered it possible for further purification though not as effective as Kojic acid (IC50 of 0.0432 mg/mL). Besides, the different bioactivities in propolis from different sites were expected due to the different flora in each location. However, further studies are needed to better understand the properties and safety aspects of selected partitioned extracts.
Knowledge of the genetic diversity of Apis spp. is important in order to provide a better understanding of breeding strategies that relate to the conservation of wild species and colony survival of farmed species. Here, honeybees of five Apis species were collected from 12 provinces throughout Thailand. After DNA extraction, 28S rRNA nuclear (710 bp) and cytochrome b (cytb) mitochondrial (520 bp) gene fragments were sequenced. Homologous sequences (nucleotide identity of over 95%) were obtained from GeneBank using the BLASTn algorithm, aligned, and analysed by maximum likelihood and Bayesian inference phylogenetics. For 28S rRNA, a low genetic variation was detected within species (haplotype diversity ranging from 0.212 to 0.394), while 19 polymorphic sites were detected between species. Although the relative haplotype diversity was high, a low nucleotide divergence was found (0.7%), with migratory species. For cytb, the sequence divergence ranged from 0.24 to 3.88% within species and 7.35 to 13.07% between species. The divergence of cytb was higher than that of 28S rRNA. A. cerana showed two distinct clades between Southern Thailand and the other regions. Groups of A. cerana (Asian cavity-nesting), A. mellifera (European cavity-nesting), A. dorsata (giant open-nesting), and A. florea and A. andreniformis (dwarf bees) were defined in the 28S rRNA and cytb tree topologies.
This research aimed to investigate the impact of heat treatment on stingless bee honey obtained by Heterotrigona itama, a commercial stingless bee found in the southern region of Thailand. Ten honey samples originating from three different forest types (mangrove forest, swamp forest, and mixed forest) were heated to 37 °C and 45 °C for 24 and 48 h and then analyzed for their physicochemical properties, total phenolic content, the flavonoid content, and antioxidant activity by radical scavenging activity on 2,2-Diphenyl-1-picrylhydrazyl (DPPH). The results showed the raw honey from mixed forest had the highest radical scavenging activity with IC50 of 43.996±0.377 mg/ml. In addition, this honey sample also exhibited the highest phenolic and flavonoid contents with 89.916±0.358 mg GAE /100 g of honey and 58.093±0.294 mg QE/ 100 g of honey, respectively. After heat treatment, the honey samples showed little change in physicochemical properties when compared to raw honey samples. After incubation at 45 °C for 48 hours, the moisture content decreased 27.93±0.17 to 20.14±0.34 g/100 g. Interestingly, heat treatment at 37 °C and 45 °C did not affect the total phenolic, flavonoid contents, and antioxidant activities (p > 0.05) in the honey samples. While heat treatment aids in keeping the physicochemical and bioactive properties of dehydrated honey, it can be concluded that the proposed method can be employed as an alternate method for preserving honey from stingless bees.
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