Honey and propolis are easily accessible honeybee products which are becoming increasingly popular due to their potential role in contributing to human health [1]. Honey is the organic, natural sugar, produced from the nectar and exudation of plant by honey bees [2]. It is mainly composed by sugars (fructose and glucose), water and also contains small amounts of other constituents like proteins, vitamins, minerals, flavonoids, phenolic acids, enzymes, numerous volatile compounds and other natural products [3-5]. Propolis is a resinous material that bees collect from the buds and bark of some trees, especially coniferous trees [6]. The chemical composition of propolis is very complex and depends on the specificity of the local flora and thus on the geographic and climatic characteristics of this site. This fact results in the striking diversity of propolis chemical composition [7]. The antioxidant properties of honey and propolis believed to be at the heart of their polyphenolic compounds. The Algerian natural honey and propolis are thought to be of different varieties due to the unique and highly diverse flora of the country because of its rich variety of environmental features ranging from semi-desert to mountain forests and its wide range of ecological, edaphic, and climatic conditions [8-11].

The objectives of the present study were to determine the total phenolic content, total flavonoid content and antioxidant activities of the two honey (Zizyphys lotus and Peganum harmala) and one propolis samples, collected from the region of Laghouat (South of Algeria). The total phenolic content was estimated by FolinCiocalteau method and total flavonoid content was estimated by AlCl3 method respectively. Finally, the antioxidant activities of all samples were evaluated by DPPH assay and Reducing power.

Honey and propolis were collected starting in December 2016 until February 2017 from the region of Laghouat (South of Algeria) and were kept in the dark at 4°C until used.

Propolis (1g) was chopped into small pieces and extracted with 10 ml 80% ethanol and left for 96 h at 37ºC, under agitation (200 rpm) and then filtered and evaporated until a constant volume. The same procedure was repeated with ethanol 50 % for honey.

Total phenolics (TPC) of the samples were determined spectrophotometrically by the Folin-Ciocalteu reagent according to the method of Singleton & Rossi [12]. The content of total phenolics was expressed as mg of gallic acid equivalents per 100g (mg GAE/ 100g) of sample. All determinations were carried out in triplicates.

Total flavonoids (TFC) of the samples were measured by the aluminum chloride spectrophotometric assay [13]. Total flavonoids content was expressed as mg of rutin equivalents per 100g (mg RE/ 100g) of sample. All determinations were carried out in triplicates.

Protein content was determined by spectrometry at 750 nm by the method of Lowry et al. [14] with bovine serum albumin as the standard. The results were expressed as mg/100g of sample. All determinations were carried out in triplicates.

Reduction of the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical by extracts followed the procedure of Brand-Williams, et al. [15]. The scavenging ability of the samples was expressed as IC50 value, which is the effective concentration at which 50% of DPPH radicals were scavenged. The IC50 values were calculated from the relationship curve of scavenging activities (%) versus concentrations of respective sample.

The reducing power of the samples was determined by the method of Oyaizu, et al. [16]. Ascorbic acid was used as a reference standard. The increase in absorbance provided an indication of higher reducing power of the samples being analyzed.

All data were presented as means ± S.D. Statistical analysis of all the assay results was done using the Microsoft Excel program (2007).

Table 1 shows the total polyphenol, flavonoids, protein contents and antioxidant activities of honey and propolis samples. While the amount of phenolic compounds is very low in honey samples (38–86 mg/100g sample), it is very high in propolis sample (2385 mg/100g sample). Ahn, et al. & Kumazawa, et al. [13,17] reported that the polyphenols content of ethanolic extracts from European and Chinese propolis were approximately 200–300 mg/g samples. Besides, the honey phenolic contents have been found higher than other floral honeys in many investigations [18,19]. The protein content of honey and propolis samples was between 85 and 133 mg/100g for honey samples and 1177mg/100g for propolis (Table1). Relatively higher protein levels ranging from 370 to 940 mg/g have also been reported in Algerian honey samples [20], whereas for honey samples from India, the content was reported to be lower (40 mg/g). The protein content can be attributed to the presence of different types of enzymes and other derived products that were introduced by the bees from the flower nectar. Protein levels in honey are dependent on the type of flora on which the bees forage [21]. The antioxidant activities of the honey and propolis samples were examined by comparing them with the known antioxidants (Ascorbic acid, BHT and Trolox) by employing the following two complementary in vitro assays: Reducing power and DPPH radical scavenging. Ascorbic acid has been used as a natural antioxidant and BHT and Trolox as artificial standard antioxidants. The propolis extracts had stronger antioxidant activity than the same floral honey extracts.

DPPH scavenging is widely used to test the free radical-scavenging activity of several natural products [13]. DPPH is a stable free radical and any molecule that can donate an electron or hydrogen to DPPH· can react with it and bleach the DPPH· absorption at 517 nm [22]. There is a reverse correlation between IC50 values and DPPH scavenging activity. The DPPH radical-scavenging activity of the samples is presented in Table 1.The radical-scavenging activities of the samples and the standards were found to be in the order of Ascorbic acid > BHT > Propolis >Trolox > Honey 2> Honey 1. The better DPPH scavenging activity may be related to the higher phenolic contents. Although the honey and propolis samples may be said to have a superior level of antioxidant activity, it is not convenient to compare our individual results with literature data due to the lack of standardization in the methods. FRAP is a widely used method for antioxidant determination and has been used for the assessment of the antioxidant and reducing power of honey [19]. The FRAP assay gives a direct estimation of the antioxidants or reductants present in a sample based on its ability to reduce the Fe3+/Fe2+ couple. The mean TEAC value of the honey samples was 0.30 the highest was 0.32 (Honey 1), and the lowest was 0.0015 (Propolis) (Table1).

The evidence about the antioxidant activity of honey and propolis and its relationship with total polyphenol content, and especially flavonoid concentration, is numerours. Honey and other bee products, such as royal jelly and propolis may be used as functional foods because of their naturally high antioxidant potential. Apart from sugars, honey contains many minor components with antioxidant activity, among them amino acids and proteins, carotenes, phenolic compounds and flavonoids, ascorbic acid, organic acids, and Maillard reaction products [18,23]. According to Aljadi & Kamaruddin [19], the antioxidant capacity of honey and propolis is due to the content of phenolic compounds and flavonoids, and there is a high correlation between them and the antioxidant capacity of honey, although a synergism between several compounds is present [24,25]. Propolis also contains amino acids, phenolic acids, flavonoids, terpenes, steroids, aldehydes, and ketones which account for its antioxidant activity [26].

As a conclusion, total phenolic ; flavonoids, protein contents and antioxidant activities of the propolis sample were higher than the same-floral honey samples. Thus, propolis and honeys may protect humans from deleterious oxidative processes as a result of their antioxidative activity. Because of their high phenolic constituents, they may also possess anticancer activities. The polyphenolic-rich natural products such as honey and propolis can be suggested for regular consumption and use in food industries.

Table 1: The total polyphenol, flavonoid and protein contents of honey and propolis samples.