D fructose

2‐HPA, 3‐HPA, 4‐HPA, l‐phenylalanine and homogentisic acid were purchased from Sigma‐Aldrich (Steinheim, Germany). PA, l‐tyrosine, d(‐)‐fructose and l(+)‐arabinose were purchased from Merck (Darmstadt, Germany).

d-(−)-fructose, soluble starch (p.a.), sodium azide (> 99%), potassium iodate (99.5%) were acquired from Merck (Darmstadt, Germany). Acarbose, aminoguanidine hydrochloride (AMG, ≥ 98%), bovine serum albumin (BSA, ≥ 98%), intestinal acetone powder from rat source of α-glucosidase, α-amylase from porcine pancreas (type VI-B), lipase (type II; from porcine pancreas), dl-glyceraldehyde (≥ 98%), β-mercaptoethanol (≥ 99%), sodium carbonate (100%), p-nitrophenyl-α-d-glucopyranoside (α-pNPG), p-nitrophenyl butyrate (pNPB), orlistat and d-(−)-ribose (≥ 99%) were acquired from Sigma-Aldrich (St. Louis, MO, USA). Human aldose reductase (HAR) was purchased from Prozomix (Northumberland, UK) and β-nicotinamide adenine dinucleotide reduced tetrasodium salt hydrate (NADPH, ≥ 97%) from Calbiochem (San Diego, CA, USA). 1-Deoxynojirimycin (1-DNJ; 95–99%) was obtained from Biopurify phytochemicals LTD (Chengdu, China). (+)-Catechin hydrated (> 99%) and quercetin dihydrate (> 99%) were acquired from Extrasynthese (Genay, France) and Riedel-de Haen, respectively.

Polyethylene glycol, poly (vinyl alcohol) 87%–89% hydrolyzed, coconut oil, ethylcellulose, hydrochloric acid, anhydrous sodium phosphate dibasic, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), Trypsin—EDTA, trypan blue, dimethylsulfoxide (DMSO), camptothecin, potassium dihydrogen phosphate monobasic buffer salt, isoniazid, and phosphate buffered saline powder were purchased from Sigma Chemical Company (St. Louis, MO, USA). D-fructose was obtained from Merck Chemicals (Darmstadt, Germany). The human breast cancer (MCF-7) cell line was purchased from American Type Culture Collection (ATCC, Manassas, VA, USA). Dulbecco’s Modified Eagle’s Medium (DMEM) and fetal bovine serum (FBS) were procured from BD Biosciences (San Jose, CA, USA). All other reagents utilized were of analytical grade and used as received from the supplier.

HPLC-grade methanol (MeOH), HPLC-grade acetonitrile (ACN), dimethyl sulfoxide (DMSO), sodium carbonate (Na₂CO₃ > 99%), aluminium chloride (AlCl₃ > 99%), D-(+)-glucose, DL-lactic acid (90%), choline chloride (98%), and standard compounds: ethyl-o-vanillin - ISTD (99%), diosmin (95%), rutin (99%), chrysin (99%), morin hydrate (95%), myricetin ( > 96%), apigenin (97%), (–)-epicatechin (99%), (+)-catechin, vanillic acid (97%), syringic acid (97%), trans-p-coumaric acid (98%), o-coumaric acid (98%), ferulic acid (98%), and rosmarinic acid (97%) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Chlorogenic acid (99%), trans-cinnamic acid (98%), quercetin hydrate (99%) and flavone (99%) were supplied by Acros Organics (Belgium). Protocatehuic acid (99%), caffeic acid (99%) and kaempferol as well as Folin–Ciocalteu phenol reagent (2N), D-(–)-fructose and sodium acetate (CH₃COONa) were supplied by Merck (Germany). Gallic acid (99%) was purchased from Carlo Erba (Italy). Ultrapure water (resistance above 18 MΩ cm) used was obtained from a Milli-Q water purification system.

The fructose content of mosquitoes was quantified using the cold anthrone assay [27 (link)] with modifications [21 (link)]. In brief, mosquitoes were homogenised using a TissueLyser II (Qiagen, USA) at 30 r.p.m. for 2 min with 50 μL of 2% sodium sulphate solution and glass beads (3 mm; Merck). Fructose was extracted by adding 375 μL of chloroform:methanol (1:2) solution, vortexing briefly and centrifuging for 15 min at 200 g. To quantify fructose, 10 μL of extract (or standards) was transferred to duplicate wells of a 96-well microplate and mixed with 240 μL of anthrone solution (containing 67.9 μL distilled water, 172.1 μL sulphuric acid, and 0.339 mg anthrone per sample). The plates were covered and incubated in the dark at room temperature for 90 min and absorbance was measured at 630 nm using a microplate reader (POLARstar Omega; BMG Labtech, Mornington, Australia). Standards were chosen to cover the range of the analyte, i.e. 0, 0.078, 0.156, 0.3125 and 0.625 μg/µL of D-(−)-fructose (≥ 99%; Merck) in 25% EtOH, produced once by serial dilution and stored at − 30 °C. The laboratory controls were 2-day-old female Ae. aegypti fed 50% fructose (positive controls) and 2-day-old female sugar-starved Ae. aegypti (negative controls).

Twelve sugars (L-arabinose, D-fructose, D-galactose, D-glucose, D-maltose, D-mannose, D-mannitol (Merck, Belgium), D-sorbitol, L-rhamnose, L-fucose, D-xylose, and D-ribose (Senn Chemicals, Switzeland) and DHA were tested as possible co-substrate for the production of PDO from glycerol. The medium used for the sugar tests is described by Maervoet et al. [12 (link)]. In order to find the optimal glucose/glycerol molar ratio, the same cultivation medium was used with 33 mM glucose and several glycerol concentrations. Molar ratios of 1, 0.33, 0.2, and 0.1 mol glucose/mol glycerol were tested. The cultivation conditions for these tests are described in Maervoet et al. [12 (link)]. Standard deviations were calculated from two independent experiments.