Phytochemical characterization of flowers

It is well known that food which is rich in natural antioxidants leads to a limited incidence of cardio and cerebro-vascular diseases (Hertog et al., 1993). Natural anti-oxidants are present in compounds belonging to several classes of phytochemical components such as phenols, flavonoids carotenoids and tannins (Vincenzo et al., 1999). These compounds are able to scavenge free radicals such as oxygen, hydroxyl or liquid peroxyl radical in plasma (Hertog et al., 1993; Miller et al., 2000a,b,; Frei et al., 1988). Besides, free radical oxidation of the lipid components in foods is a major problem for food manufacturers and thus the early attempts to measure antioxidative activity were mainly focused on lipid protection (Frankel, 1980). So far synthetic materials such as butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) are being applied to reduce problems associated with lipid oxidation in foods. However reports on the harmful effects of these compounds call for research into the use of plant products as alternatives to synthetic additives (Adegoke and Odesola, 1996; Mclellan et al., 1995; Adegoke and GopalaKrishna, 1998). The potent sources of natural antioxidants are spices and herbs (Caraleuro et al., 2006; Helle et al., 2004; Rita et al., 2009; Fasoyiro and Adegoke, 2007). Aframomum danielli is a spice belonging to the genus Aframomum and the family zingiberaceae. The seed of A. danielli plant has been found to contain phytochemicals (Fasoyiro and Adegoke, 2007). 

All chemicals used in this study were of analytical grade, obtained from fluka chemical. 

The leaf, flower, stem and roots of freshly harvested plant of A. danielli were collected from a farmer in Ibadan, Oyo State, Nigeria, sun dried for a week and trimmed to remove extraneous materials. The samples were pulverized using a warring blender. The ground spice was sieved (200μm aperture sieve) and packaged in a polythene bag till used. 

This was carried out on ground spice using the method described by Trease and Evans (2002). Preparation of extracts from powder of A. danielli leaf, flower, stem and root: 200 g of each of the powdered, A. danielli samples was percolated with 1000 mi of 100% methanol at room temperature for 24 h and filtered. The extracts obtained were concentrated in vacuo at 50°C to give the crude extracts of the plant parts.

Table 1. Phytochemical screening of plant parts.

 

This was carried out using the method described by Hostettman et al. (1985). Five fractions were collected for each of the leaf and flower, while two were collected for each of the stem and root. 

These were determined by 1,1,-diphenyl-1, 2-picrylhydrazyl (DPPH) assay as described by Aderogba et al. (2004). Ascobic acid was used as positive control. 

15-Lipoxygenase enzyme was used for peroxidation of linoleic acid as described by Lyckander and malternel (1992). 

This was carried out by Agar diffusion method (Hugo and Russel, 1983). The test organisms were: Bacillus subtilis, staphylococcus aureus, Escherichia coli ,Salmonella enteriditis, Candida albicans and Aspergillus flavus. Ampicillin (100 ppm) and Tioconazole (100 ppm) were used as controls. 

The phytochemical screening of A. danielli leaf, flower, stem and root revealed the presence of phytochemicals which are of anti-oxidative and anti-microbial interest. The result of phytochemical screening is presented in Table 1. A. danielli parts tested positive to Meyer's test and confirmatory Dragendroff's test indicated the presence of alkaloids. The flower and roots were tested positive for cardenolides; Keller-killanis and Kede's test indicated the presence of sugar as glycosides. Flavones (flavonoids) were present in flower and root but not as intense in leaf. 

The result of the anti-oxidant activities of the fractions is given in Table 2. Flower fraction FF5 had average anti-oxidant activities of 93.38 ± 3.15, 91.54 ± 1.36 and 85.94 ± 0.27% at concentrations of 250, 500 and 750 μg/ml respectively. The leaf, stem and root fractions are not so potent in scavenging DPPH radicals; the leaf, stem and root showed maximum anti-oxidant activities of 53.92 ± 0.11, 53.84 ± 0.39 and 52.69 ± 0.71% respectively at concentrations of 750 μg/ml on DPPH free radicals. The activities in leaf, stem and root fractions in this assay may be caused by lack of hydrogen donating capacity of the leaf, stem and root. 

The leaf fractions showed higher anti-oxidant activities towards 15-LO enzyme in comparism to DPPH radicals. The flower fraction FF5 followed closely by leaf fraction LF4 had high antioxidant activities values of 87.11 ± 5.13 and 82.51 ± 2.62%, respectively. This could be due to the fact that involvement of proton donation from the active compounds may be less important for 15-LO inhibition (Lyckander and Malternal, 1992).

Table 2. Anti-oxidant activities of purified fractions of A. danielli flower, leaf, stem and root on 1,1-diphemyl 1,2 picrylhydrazy (DPPH) free radical at various concentrations.

Table 3. Inhibition of 15-lipoxygenase (15-LO) enzyme by A. danielli flower leaf stem and root fractions.

Table 4 shows the zones of inhibition of the partially purified fractions A. danielli plant on some food borne pathogens in comparison with ampicillin. Flower fraction FF₅ had the highest antimicrobial activity on B. subtilis, S. aureus and Salmonella enteridits among all the fractions. The flower fraction FF₅ and root fraction RF₂ had higher antimicrobial activity on S. enteridits in comparison with ampicillin. Root fraction RF₂ had higher activity on E. coli compared to ampicillin, leaf fraction F₁ had the least activity on the pathogenic bacteria. Table 5 shows the zones of inhibition of A. danielli plant parts on Candida albicaus and A. flavus. Flower fraction FF₅ had higher antimicrobial activities on C. albicans and A. flavus compared to Tioconazole. Stem fraction SF₁ and root fraction RF₁ had the least activities on C. abbicaus and flavus, respectively.

Table 4. Zones of inhibitions (mm) of flower, leaf, root and stem fractions on some food borne pathogens at 750 μg/ml.

Table 5. Zones of inhibition (mm) of A. danielli flower, leaf root and stem fractions on A. flavus and C. albicans at 750 μg/ml.

This study had been able to highlight some of the phytochemical components present in the leaf, flower, stem and root of A. danielli plants. This showed that this plant parts could serve as antioxidant and anti-microbial agent in food when purified and concentrated. 

The authors thank Dr. B. Torto of ICIPE-African Insect Science for Food and Health Nairobi, Kenya for his interest and encouragement in this research work. 

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