## 3 Significance of Volatile Organic Compounds in Honey
### Biomedical Activities of Honey and Contribution from Its Volatile Constituents
Albeit, their antibacterial activity should not be overlooked since the composition of phytochemical has an influence on the biological activity of honey; usually, the same compounds have antioxidant and antimicrobial activity therefore may contribute in the efficacy of honey in therapeutic uses. It is possible therefore to assert that the antimicrobial factors (peroxide and non-peroxide) in honey could be acting in synergy in a bid to inhibit the growth of micro-organisms. Volatiles in honeys occur most frequently in very low concentrations and are a complicated mixture of substances with various physicochemical properties and levels of stability. On that account, it is especially essential to select a suitable extraction technique [6]. In a nutshell, the bioavailability of these compounds would depend on the extraction technique which determines the type of compounds isolated as well as influences the concentration yield. For example, [PERSON] _et al_. [31] investigated VOCs in _Amorpha fruitcosa_ honey samples using two methods, HS-SPME and USE. The HS of the honey was dominated by 2-phenylethanol (38.3-58.4%), whilst 2-Phenylethanol (10.5-16.8%) and methyl syringae (5.8-8.2%) were the major compounds of ultrasonic solvent extracts. Furthermore, the scavenging abilities of the series of concentrations of honey ultrasound solvent extracts and the corresponding honey samples was tested by a DPPH (1,1-diphenyl-2-picrylhydrazyl) assay. Approximately 25 times lower concentration ranges (up to 2 g/L) of the extracts exhibited significantly higher free radical scavenging potential with respect to the honey samples. In another study investigating the VOCs of two oak honey, [PERSON] _et al_. [58] reported terpen as the most volatile organic headspace compounds. Also, the antioxidant capacity (FRAP assay) of honeydew samples was 4.8 and 16.1 mmol Fe\({}^{2+}\)/kg, while the solvent mixture extracts showed antioxidant activity of 374.5 and 955.9 Fe\({}^{2+}\)/kg, respectively. In addition, the ascorbic acid content of honey ranges from 0.5 to 6.5 mg/100 g with an average of 2.4 mg/100 g or 5 mg/mL. However, some specific varieties of honey have been reported to contain as much as 75-150 mg ascorbic acid per 100 g, while most honey contain less than 5 mg/100 g. The gastrointestinal absorption of ascorbic acid occurs through an active transport process, as well as through passive diffusion [59]. Maillard reaction, a non-enzymic browning reaction occurs between sugars and free amino acids during thermal treatment of honey. It is believed that Maillard reaction products (MRPs) are acting as antioxidants [60]. Hydroxymethylfurfural (HMF) is one of the major intermediate products of Maillard reaction which is formed from the condensation of sugars in the presence of an amino acid during processing, prolonged storage or excessive heating of honey [61]. Its maximum concentration is 15 mg/kg in honey and is regulated by law. Both compounds (ascorbic acid and HMF) are known antioxidants in honey with the potential to scavenge for free superoxide and reactive oxygen metabolites (radicals). In a study conducted by [PERSON] _et al_. [60] on the effects of prolonged heating on antioxidant activity and color of honey reported that the antioxidative activity increases linearly with increasing temperature. This observation was previously demonstrated by the work of [PERSON] _et al_. [62] on the antioxidative effect of MRPs formed from honey at different reaction times. Furthermore, [PERSON] and [PERSON] [63] in a study to explore the antioxidative characteristic of tomato fruit showed a significant linear correlation of antioxidativeative potential with lycopene, polyphenol and hydroxymethylfurfural content that increased continuously during ripening period. Other MRPs namely maltol (3-hydroxy-2-methyl-4 Hpyran-4-one), isomaltol [1-(3-hydroxy-2-furanyl)ethanoneone], 5-hydroxy, 5,6-dihydromaltol, 4-hydroxy-5-methyl-3-(2\(H\))-furanone are potential precursors for antioxidants [62].