2.1. Ferric reducing/antioxidant power (FRAP) assay
The FRAP assay measures the reducing potential of an antioxidant that reacts with a ferric tripyridyltriazine (Fe
3+ - TPTZ) complex to produce a colored ferrous tripyridyltriazine (Fe
2+ - TPTZ) [
19,
20]. Generally, the reducing properties are associated with the presence of compounds, which exert their action by breaking the free radical chair through the donation of a hydrogen atom [
21,
22]. The FRAP values of the two types of Malaysian honey dissolved in water or methanol in the concentration range of 0.1–0.4 g/mL are shown in (
Table 1). In general, an increase in the concentration of honey resulted in significant (p < 0.05) increases in the ferric reducing antioxidant power (FRAP) for all honey samples. This result is similar to the study of Malaysian herbs performed by Huda-Faujan
et al. [
23], who found that all of the herbs extracts showed increased reducing ability as the concentration of extracts were increased.
Table 1.
Ferric Reducing Antioxidant Power (FRAP) values of Gelam and Nenas honeys before and after irradiation.
Table 1.
Ferric Reducing Antioxidant Power (FRAP) values of Gelam and Nenas honeys before and after irradiation.
Concentration (g/mL) | Honey Dissolved in Distilled water |
---|
NNI | NI | GNI | GI |
---|
0.1 | 105.64 ± 2.03 a,c | 200.74 ± 2.51 b,c | 210.08 ± 2.68 a,d | 283.24 ± 8.44 b,d |
0.2 | 179.19 ± 5.19 a,c | 354.07 ± 9.36 b,c | 367.37 ± 13.1 a,d | 571.13 ± 1.64 b,d |
0.3 | 255.37 ± 4.56 a,c | 513.40 ± 8.32 b,c | 526.80 ± 12.0 a,d | 909.27 ± 16.8 b,d |
0.4 | 311.4 ± 7.97 a,c | 660.20 ± 68.5 b,c | 689.37 ± 23.6 a,d | 1108.9 ± 28.5 b,d |
Concentration (g/mL) | Honey Dissolved in Methanol |
NNI | NI | GNI | GI |
0.1 | 79.07 ± 0.81 a,c | 182.93 ± 6.05 b,c | 188.97 ± 5.44 a,d | 270.70 ± 13.8 b,d |
0.2 | 147.83 ± 0.60 a,c | 309.60 ± 15.8 b,c | 310.72 ± 11.6 a,d | 587.60 ± 40.7 b,d |
0.3 | 242.50 ± 5.68 a,c | 458.70 ± 22.7 b,c | 508.77 ± 39.0 a,d | 868.03 ± 14.5 b,d |
0.4 | 283.30 ± 21.9 a,c | 546.50 ± 34.6 b,c | 618.30 ± 26.1 a,d | 1091.6 ± 44.9 b,d |
When comparing the FRAP values between different solvents, we found that both methanol and water gave similar antioxidant reducing power for both types of honey. Generally, the FRAP value of the Gelam honey was found to be significantly (p < 0.05) higher than that of the Nenas honey in all concentrations and solvents. Aljadi
et al. [
10] also reported that Gelam honey has a significantly higher FRAP value than coconut honey. We also observed that both irradiated Gelam and Nenas honeys indicated a significantly (p < 0.05) higher FRAP value compared to their non-irradiated counterparts in both solvents. Gamma irradiation is a method of decontamination for food and herbal materials [
16,
17]. It has been used to prevent microbial and bacterial contamination in honey. Molan
et al. [
18] and Postmes
et al. [
24] reported that irradiation rendered the honey sterile without affecting its antibacterial activity.
To our knowledge, no studies have reported on the effect of gamma-irradiation on the antioxidant properties of honey. Song
et al. [
25] reported that the antioxidant capacity of irradiated carrot juice was higher than that of the non-irradiated juice; while Stajner
et al. [
26] found higher antioxidant capacities in irradiated versus non-irradiated soya. The increase in antioxidant activity following irradiation might be due to the degradation of some high molecular weight components, and changing the solubility of these compounds in the test solvents gave rise to more phenolic compounds [
27].
2.2. The free radical-scavenging activity
One of the mechanisms to investigate antioxidant activity is to study the scavenging effect on proton radicals. In the present study, investigation of the total antioxidant capacity was measured as the cumulative capacity of the compounds in the sample that can scavenge free radicals using the DPPH reaction. The presence of antioxidants in the sample leads to the disappearance of DPPH radical chromogens, which can be detected spectrophotometrically at 517 nm [
28].
The radical scavenging activities of the honey samples were analyzed in water and methanol solvents using 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH). For both types of honey, the scavenging activity was found to increase significantly (p < 0.05) with increasing concentrations in both solvents (
Table 2). As seen in
Table 2 both types of honey Gelam and Nenas (irradiated and nonirradiated) have high scavenging activities in both solvents. Gelam honey, dissolved in both solvents and at all concentrations, has a significantly (p < 0.05) higher ability to scavenge the free radical compared to Nenas honey.
Table 2.
Radical scavenging activity (% inhibition) of Gelam and Nenas honeys before and after irradiation.
Table 2.
Radical scavenging activity (% inhibition) of Gelam and Nenas honeys before and after irradiation.
Concentration (g/mL) | Honey dissolved in distilled water |
---|
NNI | NI | GNI | GI |
---|
0.1 | 3.69 ± 0.07 a,c | 18.00 ± 0.21 b,c | 31.46 ± 0.36 a,d,e | 54.60 ± 1.82 b,d,e |
0.2 | 6.24 ± 3.25 a,c | 28.63 ± 5.98 b,c | 53.58 ± 1.57 a,d,e | 73.13 ± 1.08 b,d,e |
0.3 | 9.07 ± 1.25 a,c,e | 35.71 ± 0.37 b,c | 69.39 ± 0.74 a,d,e | 77.93 ± 0.49 b,d,e |
0.4 | 28.67 ± 0.95 a,c,e | 52.79 ± 0.82 b,c | 76.29 ± 0.58 a,d,e | 82.68 ± 0.80 b,d,e |
Concentration (g/mL) | Honey dissolved in methanol |
NNI | NI | GNI | GI |
0.1 | 1.66 ± 1.12 a,c | 16.61 ± 1.85 b,c | 24.37 ± 3.98 a,d,f | 51.51 ± 0.42 b,d,f |
0.2 | 3.75 ± 1.26 a,c | 25.96 ± 4.98 b,c | 42.61 ± 2.40 a,d,f | 64.44 ± 0.14 b,d,f |
0.3 | 5.11 ± 1.86 a,c,f | 33.97 ± 1.31 b,c | 62.33 ± 4.15 a,d,f | 68.52 ± 1.77 b,d,f |
0.4 | 17.74 ± 1.33 a,c,f | 51.04 ± 0.22 b,c | 68.22 ± 0.94 a,d,f | 79.26 ± 0.14 b,d,f |
Gamma-irradiation caused a significant (p < 0.05) increase in the free radical-scavenging activity for both Gelam and Nenas honeys at all concentrations and solvents tested. Many researchers [
4,
6,
13,
29,
30,
31,
32,
33,
34] have demonstrated the high scavenging activity of honey by various assays such as DPPH, ABTS, ONOO
- and NBT; however, none of them have compared the antioxidant properties of honey between the irradiated and nonirradiated forms. We found reports on the effects of irradiation on the antioxidant properties of other food products besides honey. Jo
et al. [
35] reported that irradiation (10 and 20 kGy) on green tea extracts increased its antioxidant properties while Khattak
et al. [
36] and Stajner
et al. [
26] found that irradiation increased the antioxidant properties of the
Glycyrrhiza glabra root and soybean, respectively. According to Khattak
et al. [
27], gamma irradiation enhanced the free radical scavenging activity in
Nigella sativa seeds. On the contrary, Lampart-Szcrapa
et al. [
37] reported that increasing doses of irradiation decreased the antioxidant effects of lupin seed extracts.
2.3. Total Flavonoid contents (TFC)
The total flavonoid contents in Gelam and Nenas honey dissolved in methanol are shown in (
Table 3). Total flavonoid contents increased significantly (p < 0.05) with increasing honey concentrations.
Table 3.
Flavonoid contents (mg Rutin equivalent/100 g) of Gelam and Nenas honeys before and after irradiation.
Table 3.
Flavonoid contents (mg Rutin equivalent/100 g) of Gelam and Nenas honeys before and after irradiation.
Concentration (g/mL) | NNI | NI | GNI | GI |
---|
0.1 | 1.23 ± 0.19 a | 1.96 ± 0.11 b,c | 1.47 ± 0.03 a | 2.93 ± 0.13 b,d |
0.2 | 1.86 ± 0.39 a,c | 2.89 ± 0.16 b,c | 3.38 ± 0.02 a,d | 5.05 ± 0.08 b,d |
0.3 | 3.79 ± 0.10 a,c | 4.23 ± 0.02 b,c | 4.24 ± 0.05 a,d | 5.68 ± 0.14 b,d |
0.4 | 4.52 ± 0.01 c | 4.79 ± 0.15 c | 4.94 ± 0.26 a,d | 6.92 ± 0.81 b,d |
Gelam honey has a significantly (p < 0.05) higher amount of flavonoids than Nenas honey. Similarly, we found that irradiated Gelam and Nenas honeys exhibited a significantly (p < 0.05) higher content of flavonoids than their nonirradiated counterparts.
Previous studies have reported high flavonoid contents in different kinds of honey such as Portuguese, Burkina Fasan and Cuban honeys [
6,
29,
38]. Flavonoids are recognized for their high pharmacological activities as radical scavengers [
39]. Recent interest in these substances has been stimulated by the potential health benefits arising from their antioxidant activities and free radical scavenging capacities in coronary heart disease and cancer [
40].
2.4. Total phenolic contents (TPC)
Table 4 shows the total phenolic contents of Gelam and Nenas honey. Total phenolic contents increased significantly with increasing honey concentrations for both Gelam and Nenas honeys in both solvents (water and methanol). There were no significant differences of total phenolic contents between water and methanol solvents for either Gelam or Nenas honey at any of the concentrations tested. However, Gelam honey exhibited significantly (p < 0.05) higher total phenolic contents than Nenas honey at all tested concentrations for both solvents. The total phenolic contents vary between different honey samples depending on the geographical location of the different floral sources, such as Malaysia, Burkina Faso, Turkey and Croatia [
4,
10,
29,
33,
41].
Table 4.
Total phenolic contents (mg Rutin equivalent/100 g) of Gelam and Nenas honeys before and after irradiation.
Table 4.
Total phenolic contents (mg Rutin equivalent/100 g) of Gelam and Nenas honeys before and after irradiation.
Concentration (g/mL) | Honey Dissolved in Distilled water |
---|
NNI | NI | GNI | GI |
---|
0.1 | 3.62 ± 0.18 a,c | 9.66 ± 0.32 b,c | 8.47 ± 0.20 a,d | 18.78 ± 1.60 b,d |
0.2 | 9.17 ± 1.00 a,c | 19.86 ± 0.90 b,c,e | 21.09 ± 0.37 a,d,e | 42.40 ± 0.34 b,d |
0.3 | 15.42 ± 0.35 a,c | 28.62 ± 1.27 b,c | 30.32 ± 0.77 a,d | 56.59 ± 1.24 b,d,e |
0.4 | 21.60 ± 0.45 a,c | 38.91 ± 1.64 b,c | 41.76 ± 0.84 a,d,e | 72.64 ± 0.89 b,d |
Concentration (g/mL) | Honey Dissolved in Methanol |
NNI | NI | GNI | GI |
0.1 | 3.43 ± 0.31 a,c | 10.0 ± 0.91 b,c | 9.44 ± 1.69 a,d | 19.72 ± 1.44 b,d |
0.2 | 8.65 ± 1.17 a,c | 18.11 ± 1.06 b,c,f | 22.67 ± 0.59 a,d,f | 41.80 ± 1.38 b,d |
0.3 | 15.26 ± 0.18 a,c | 29.13 ± 0.11 b,c | 29.39 ± 0.49 a,d | 51.79 ± 0.24 b,d,f |
0.4 | 21.33 ± 1.40 a,c | 37.98 ± 0.10 b,c | 35.99 ± 1.03 a,d,f | 71.51 ± 1.32 b,d |
Total phenolic contents in the irradiated honey were higher (both Gelam and Nenas) when compared with the nonirradiated honey. This could be due to radiolysis of phenolics (eg. Gallic acid, Caffeic acid,
etc.) in an aqueous solution that led to their efficient degradation to a hydroxylation effect [
42]. The increase in phenolic contents in this study correlates well with previous studies in which the ability of gamma-irradiation to increase phenolic content was observed in fresh vegetable juice [
25], soybean [
26], almond skin extracts [
43], and spices such as clove and nutmeg [
44]. However; Kim
et al. [
45] found no significant increase in the total phenolic contents in irradiated cumin when compared to that of the nonirradiated cumin, and Ahn
et al. [
46] found that an increasing dose of gamma-irradiation significantly reduces the phenolic contents in cut Chinese cabbage.
2.5. Correlation between Total phenolic contents (TPC) and antioxidant activities
To analyze the correlation between total phenolic content and antioxidant activity, we plotted the values of antioxidant activities (FRAP & DPPH) with the total phenolic content of honey (
Figure 1 and
Figure 2). A significant linear correlation was found between FRAP and DPPH values of Gelam and Nenas honey with TPC (r = 0.9899 and r = 0.855, respectively), as well as between total flavonoid content and antioxidant activity (r = 0.917 by FRAP assay, and r = 0.785 by DPPH assay). Other studies have also found good correlations between antioxidant capacities and phenolic as well as flavonoid contents, indicating that the phenolics and flavonoids are one of the major components responsible for the antioxidant activity of honey [
29,
33,
38,
47,
48]. A significant linear correlation between total flavonoid content and total phenolic content was observed in this study (r = 0.939) similar to findings of Socha
et al. [
34] who reported a significant linear correlation (r = 0.83) between total phenolic content and total flavonoid content in herb honeys.
Table 5 summarizes the findings of other researchers in comparison with those of our study regarding the antioxidant capacity and total phenolic and flavonoid contents of different types of honey from different sources. Our Malaysian honeys, Gelam and Nenas have comparatively higher antioxidant reducing power compared to honey from Croatia, and Gelam honey has a higher radical scavenging activity by DPPH compared with commercial Indian honey. The total phenolic content of Gelam honey was almost similar to Croatian and Portuguese honey while the flavonoid content was very low compared to Portuguese honey. Additionally, Malaysian Tualang honey (obtained from deep forest) also has high antioxidant reducing power compared to Croatian honey.
Figure 1.
Correlation between the ferric reducing antioxidant power (FRAP value) of combined (Gelam and Nenas) honeys and the total phenolic contents (TPC) to obtain the r = 0.9899.
Figure 1.
Correlation between the ferric reducing antioxidant power (FRAP value) of combined (Gelam and Nenas) honeys and the total phenolic contents (TPC) to obtain the r = 0.9899.
Figure 2.
Correlation between the radical scavenging activity (% inhibition) using DPPH of combined (Gelam and Nenas) honey and total phenolic contents (TPC) to obtain the r = 0.855.
Figure 2.
Correlation between the radical scavenging activity (% inhibition) using DPPH of combined (Gelam and Nenas) honey and total phenolic contents (TPC) to obtain the r = 0.855.
Table 5.
Antioxidant properties and total phenolic and flavonoid contents for different types of honey reported by some researchers for comparison with Malaysian honey.
Table 5.
Antioxidant properties and total phenolic and flavonoid contents for different types of honey reported by some researchers for comparison with Malaysian honey.
Honey sources | Honey types | Antioxidant activity by FRAP assay (µM FeII) | Radical scavenging activity by DPPH (% inhibition) | Total phenolic contents (mg/100 g honey) | Total flavonoid contents (mg/100 g honey) |
---|
Croatian monofloral honey (Piljac-Zegarac et al., 2009) [41] | Jerusalem thorn | 113.49 ± 2.91 | - | 48.58 ± 0.95 | - |
Sunflower | 113.81 ± 9.72 | - | 54.63 ± 1.20 | - |
Sage | 121.27 ± 4.70 | - | 55.40 ± 1.14 | - |
Velebit winter | 118.57 ± 4.54 | - | 44.43 ± 2.83 | - |
Winter savory | 99.68 ± 3.99 | - | 44.17 ± 2.24 | - |
Amorpha | 23.02 ± 2.79 | - | 25.66 ± 0.99 | - |
Chestnut | 84.60 ± 2.62 | - | 43.09 ± 2.68 | - |
Linden | 73.81 ± 6.75 | - | 40.88 ± 1.05 | - |
Acasia | 12.06 ± 1.98 | - | 21.61 ± 0.63 | - |
Oilseed rape | 52.22 ± 6.14 | - | 36.92 ± 2.53 | - |
Goldenrod | 92.86 ± 1.65 | - | 49.24 ± 2.02 | - |
Northeast Portugal honey (Ferreira et al., 2009) [6] | Light | - | - | 22.61 ± 0.02 | 12.36 ± 0.01 |
Amber | - | - | 40.62 ± 1.72 | 34.27 ± 0.17 |
Dark | - | - | 72.77 ± 0.02 | 58.74 ± 0.04 |
Commercial Indian honey (Saxena et al., 2010) [32] | I | - | 64 ± 0.7 | 98 ± 1.2 | - |
II | - | 59 ± 0.5 | 47 ± 0.2 | - |
III | - | 61 ± 0.9 | 83 ± 1.1 | - |
IV | - | 44 ± 0.6 | 67 ± 0.8 | - |
V | - | 67 ± 1.1 | 91 ± 1.4 | - |
VI | - | 71 ± 1.3 | 94 ± 0.8 | - |
VII | - | 48 ± 0.8 | 99 ± 1.3 | - |
Malaysian Honey (Mohamed et al., 2010); Saba et al., 2010) [30,49] | Tualang | 322.7 ± 1.7 | 41.3 ± 0.78 | 25.17 ± 0.79 | - |
Gelam GNI (0.4 g/mL) | 689.37 ± 23.6 | 76.29 ± 0.58 | 41.76 ± 0.84 | 2.64 ± 0.12 |
Nenas NNI (0.4 g/mL) | 311.4 ± 7.97 | 28.67 ± 0.95 | 21.60 ± 0.45 | 1.97 ± 0.21 |
2.6. Identification and quantification of phenolic compounds in Malaysian honey by HPLC
Solid phase extraction (SPE), using C
18 cartridges, were used to extract and recover phenolic compounds from honey. The recoveries were good for all standard phenolic compounds eluted from SPE, at 290 nm for phenol acids and 340 nm for flavonoids. The recoveries of phenolic acid standards were 71.5–98.8% while the flavonoid standards were 71.94–90.74%, indicating the suitability of this procedure for the recovery of phenolics in honey [
50].
Figure 3 and
Figure 4 show the UV absorption chromatograms of the two types of Malaysian honey (Gelam and Nenas) isolated by SPE at 290 nm and 340 nm. The concentrations of phenolic compounds in Malaysian honey are summarized in
Table 6. The chromatograms of the extract samples from Malaysian honey showed a number of phenolic acids which absorb more strongly at 290 nm and flavonoids which absorb strongest at 340 nm [
51]. Caffeic acid, chlorogenic acid,
p-coumaric acid, ellagic acid, quercetin and hesperetin were identified in both types of honey. On the other hand, gallic acid, ferulic acid and chrysin were identified in Gelam honey while rutin was identified only in Nenas honey. Generally, Gelam honey contains significantly higher quantity of phenolic compounds than Nenas honey as calculated from the peak areas. However, there is no significant difference between both irradiated Gelam and Nenas honeys compared to non-irradiated honey. There is no information available on the effect of radiation on the phenolic compounds in honey. However; for some plant materials, diverse effects of radiation have been reported on total phenolic contents. Lee
et al. [
52] found increased total phenolic contents in tamarind juice, while Koseki
et al. [
53] reported significant decreased phenolic contents in dehydrated rosemary after irradiation at doses between 10–30 kGy. The difference in the effect of irradiation on total phenolic content may be due to plant type, geographical, environmental condition, phenolic content composition, temperature, extraction solvent, extraction procedure, and dose of gamma irradiation [
36].
Figure 3.
Chromatogram of Phenolic acid and Flavonoids detected in Malaysian Gelam honey using HPLC-UV absorption at (I) 290 nm and (II) 340 nm. A = gallic acid, B = chlorogenic acid, C = caffeic acid, D = p-coumaric acid, E = ferulic acid, F = ellagic acid, G = quercetin, H = hesperetin, I = chrysin.
Figure 3.
Chromatogram of Phenolic acid and Flavonoids detected in Malaysian Gelam honey using HPLC-UV absorption at (I) 290 nm and (II) 340 nm. A = gallic acid, B = chlorogenic acid, C = caffeic acid, D = p-coumaric acid, E = ferulic acid, F = ellagic acid, G = quercetin, H = hesperetin, I = chrysin.
Figure 4.
Chromatogram of Phenolic acid and Flavonoids detected in Malaysian Nenas honey using HPLC-UV absorption at (I) 290 nm and (II) 340 nm. A = chlorogenic acid, B = caffeic acid, C = p-coumaric acid, D = rutin, E = ellagic acid, F = quercetin, G = hesperetin.
Figure 4.
Chromatogram of Phenolic acid and Flavonoids detected in Malaysian Nenas honey using HPLC-UV absorption at (I) 290 nm and (II) 340 nm. A = chlorogenic acid, B = caffeic acid, C = p-coumaric acid, D = rutin, E = ellagic acid, F = quercetin, G = hesperetin.
Table 6.
Concentration of phenolic compounds detected in Gelam and Nenas honeys before and after irradiation by HPLC.
Table 6.
Concentration of phenolic compounds detected in Gelam and Nenas honeys before and after irradiation by HPLC.
Phenolic Compounds | NNI | NI |
---|
Retention time (min) | µg/100 g honey at 290/340 nm | Retention time (min) | µg/100 g honey at 290/340 nm |
---|
Gallic acid | ND | ND | ND | ND |
Chlorogenic acid | 22.69 | 392.92 ± 42.22 | 22.69 | 433.73 ± 48.17 |
Caffeic acid | 23.65 | 255.84 ± 11.83 | 23.66 | 278.26 ± 30.42 |
P- Coumaric caid | 26.16 | 267.49 ± 13.99 | 26.18 | 312.10 ± 45.79 |
Ferulic caid | ND | ND | ND | ND |
Rutin | 28.52 | 1542.1 ± 60.21 | 28.50 | 1597.5 ± 125.37 |
Ellagic acid | 29.73 | 306.33 ± 15.41 | 29.71 | 339.61 ± 44.41 |
Quercetin | 37.75 | 1621.9 ± 91.11 | 37.76 | 1700.9 ± 93.97 |
Hesperetin | 39.13 | 1493.9 ± 51.73 | 39.20 | 1536.6 ± 76.38 |
Chrysin | ND | ND | ND | ND |
Phenolic Compounds | GNI | GI |
Retention time (min) | µg/100 g honey at 290/340 nm | Retention time (min) | µg/100 g honey at 290/340 nm |
Gallic acid | 7.86 | 859.43 ± 15.14 | 7.56 | 876.80 ± 7.47 |
Chlorogenic acid | 22.40 | 502.77 ± 27.98 | 22.40 | 528.08 ± 6.31 |
Caffeic acid | 23.73 | 428.84 ± 41.14 | 23.77 | 442.01 ± 32.70 |
P- Coumaric caid | 26.19 | 301.45 ± 7.06 | 26.20 | 308.31 ± 18.69 |
Ferulic caid | 26.91 | 356.93 ± 21.99 | 26.85 | 381.37 ± 17.07 |
Rutin | ND | ND | ND | ND |
Ellagic acid | 29.48 | 558.78 ± 36.68 | 29.50 | 575.67 ± 17.66 |
Quercetin | 37.50 | 1588.9 ± 31.51 | 37.35 | 1594.30 ± 38.40 |
Hesperetin | 39.20 | 1475.2 ± 5.40 | 39.21 | 1477.78 ± 1.91 |
Chrysin | 53.22 | 1498.6 ± 3.50 | 53.31 | 1504.6 ± 3.20 |
Interestingly we also found unknown compounds in both types of honey, while some of them were present in higher concentrations when determined at 290 nm and 340 nm. Most of these unknown compounds are probably phenolic acids since their absorption was found mainly at 290 nm where phenolic acids absorb maximally [
50,
51]. Gelam honey exhibited higher unknown phenolic compounds than Nenas honey, in both irradiated and non-irradiated honeys. Irradiation exerts its effects as direct and indirect mechanisms; in case of indirect mechanism, radiolysis of water results in the production of radicals such as hydrated electrons, hydroxyl radicals and hydrogen atoms [
54]. These radicals may break the glycosidic bonds that are present in honey, leading to the formation of new compounds. The increase in phenolic compounds in both gamma-irradiated honeys could be attributed to the release of phenolic compounds from glycosidic components and the degradation of the larger phenolic compounds into smaller ones by gamma irradiation [
43].