Abstract: In this study, leaves of woody plants (2-4 species) obtained in Nigeria between November and December 2001 was evaluated for their phytochemical and mineral contents using standard methods. To determine minerals, 0.5 g of each samples were dry ashed, dissolved in distilled water with few drops of conc. HCl and read on an atomic absorption spectrophotometer. Phytate and phytate P were analyzed by first extracting the samples followed by titrating with FeCl3, the values obtained were multiplied with standard factors (1.95 and 3.56, respectively) and qualitative methods were used for other tests. The study revealed presence of alkaloids, tannins, resins, saponins, flavonoids, glycosides, carbohydrate, sterols and flobatanin in most of the samples. The levels of phytate (mean = 692, SD = 212, CV% = 30.7) and phytate phosphorous (mean = 188, SD = 51, CV% = 27.4) were generally high and all leaves had more than 30% of their total phosphorus linked to phytate. These results compared with literature values. The concentrations of the mineral were found to be high. The result showed that with high phytate contents the bioavailability of minerals might be relatively low.
INTRODUCTION
Woody plants have been of wise use in Nigeria. They have contributed to sustainable development and benefit to many people especially the poor, who depend on these for their livelihoods. There are about 900 different kinds of trees in Nigeria, some are easily recognized but many can only be named with certainty when flowers or fruit as well as leaves, are available (Aju and Popoola, 2005). Fruits, barks and leaves, body are appreciated, not only for texture and flavor, but also for their chemical and nutritional properties (Abulude et al., 2004).
The woody plants are versatile material plants having a wide range of local therapeutic applications. The leaves, roots, barks and seeds are found to be active antipyretic laxative, analgesic, antifungal, antibacterial and anti-inflammatory (Faruq, 2004; Olafimihan et al., 2004; Hassan et al., 2004; Ogukwe et al., 2004). Some of the woody plants have also been reported as therapeutic foods, useful in preventing diseases such as hypertension, hypercholesterolamia and cancer (Lexicon, 1983). Fragrant gum resins obtained from some of them are sometimes used as fumigants (Hassan et al., 2004). These functional characteristics are mainly due to the presence of phytochemicals. Despite the extensive use of these woody plants, reports on detailed phytochemical investigation are scanty. Out of many potent phytochemicals, tannin, glycosides, saponin, sterol, resin, flobatannins, flavonoids, alkaloids and phytate were initially chosen for this research.
The aim of this research was to extend knowledge on mineral and phytochemical qualities of woody plant leaves. It is hoped that the results would add to composition table.
MATERIALS AND METHODS
The different varieties (2-4 species) of wood plant leaves were obtained from the Federal College of Agriculture Campus in Akure, Ondo State, Nigeria between November and December, 2004, identified and labeled (Irvine, 1961). The samples under investigation are shown in Table 1.
Experimental
One hundred gram of the leaves were washed with distilled water, oven dried
at 60°C for 6 h, then finely ground, sieved (2 mm sieve), mixed thoroughly,
stored in plastic containers and kept in ambient temperature prior analysis.
Mineral Analysis
Total phosphorus (P) was analyzed from solutions obtained by first dry-ashing
0.6 g of the samples at 550°C to constant weight and dissolving the ash
in volumetric flasks using distilled water with a few drops of concentrated
HCl. Phosphovanadomolybdate method was used for the determination (AOAC, 1990).
A Perkin Elmer atomic absorption spectrophotometer was used for the determination
of Ca, K, Na and Mg.
Phytate Analysis
Four grams of ground sample was soaked in 100 cm3 of 2% HCl for
3 h and then filtered through two layers of filter paper 25 cm3 of
the filtrate was placed in a 250 cm3 conical flask and 5 cm3
of 0.3% NH4SCN solution was added as an indicator, 53.5 cm3
of distilled water was then added to reach the proper acidity. This mixture
was titrated against FeCl3 solution, which contains about 0.00195
g of Fe iron per cm3 of FeCl3 solution. The result was
multiphed by factor 1.95 to obtain phytate P. phytate P result was multiphed
by factor 3.55 to convent to phytate.
| Table 1: | Common, scientific, family and vernacular names of the investigated woody plants |
| A Vernacular-Yoruba name | |
Phytochemical Analysis
Extraction
One hundred and fifty centiliter of water was added to 20 g of ground sample
in a conical flask. The mixture was covered and allowed to stand for 3 h with
occasional stirring. The mixture was filtered with a whatman No. 2 filter paper.
The filtrate was stored in plastic containers and kept in ambient temperature
prior to analyses (Abulude, 2001).
Test for Carbohydrate
Fehling’s Test
5 cm3 of mixture of equal volumes of Fehlings A and B was added to
2 cm3 of each extract in a test tube. The resultant mixture was boiled
for 2 min. A brick red precipitation of copper oxide was observed.
Test for Tannins
Two drops of 5% FeCl3 was added to 1 cm3 of extract. A dirty-green precipitate was observed in each extract.
Test for Glycosides
10 cm3 of 50% H2SO4 was added to 1 cm3 of each extract in a test tube. The mixture was heated in boiling water for 5 min. 10 cm3 of Fehlings solution (5 cm3of each solution A and B) was added and boiled. A brick red precipitate indicating presence of glycosides was observed.
Tests for Saponins
Frothing Test
2 cm3 of each extract in a test tube was vigorously shaken for 2
min. Frothing indicating presence of saponin was noted.
Test for Resins
5 cm3 of copper was added to 5 cm3 of each extract.
The resulting solution was shaken vigorously and allowed to separate. A green
colored precipitate indicating presence of resin was noticed.
Test for Phlobatanins
5 cm3 of distilled water was added to 5 cm3 of each
extract and boiled with 5 cm3 of 1% HCl for 2 min. No visible reaction
was obtained indicting absence of phlobatanins.
Test for Flavonoids
2 cm3 of extract was heated with 10 cm3 of ethyl acetate
on a water bath and cooled. The layers were allowed to separate and the color
of the NH3 layer noted (red coloration formed).
Test for Alkaloids
1 cm3 of 1% HCl was added to 3 cm3 of each extract
in a test tube. Each extract was treated with few drop of Meyer’s reagent.
A creamy white precipitate was observed indicating presence of alkaloids.
RESULTS
Table 2 shows total P; phytate P, phytate, phytate P expressed as percentage of total P. Phytate content ranged from 391-1108 mg 100 g-1 DM. Total P was the highest in neem leaves and lowest in pawpaw leaves.
| Table 2: | Total phosphorus (P), phytate P, phytate (mg100 g-1 DM) and phytate P (as % of total P) in the woody plant leaves examined |
| Table 3: | Phytochemical analysis of the woody plant leaves examined |
| + Present, - Absent | |
| Table 4: | Mineral composition in leaves investigated (mg100 g-1 DM) |
Phytate P expressed as percentage of total P ranged between 36% (Anacardium occidentale) and 98% (Carica papaya). Coefficient of variation in percent (CV%) of all the results were high among the samples with total P being the least (20%) while phytate (31%) showed the highest variation.
The results in Table 3 showed that carbohydrate, alkaloids, glycosides, sterols, saponins, flavonones, tannin and resin were present in most of the extracts of leaves examined. Phlobatanins was absent.
All the minerals were highly concentrated. Calcium, potassium and sodium were highly concentrated with means (mg 100 g-1) of 617 (SD = 140, CV = 23%), 617 (SD = 150, CV = 24%) and 746 (SD = 78, CV = 53%), respectively (Table 4).
DISCUSSION
The values of total P, phytate P, phytate, phytate P expressed as percentage of total P were higher than those reported for some varieties of mushrooms (Abulude et al., 2001) and some foods of major consumption in Nigeria (Adeyeye et al., 2000). Levels of phytate were comparable to levels reported for vegetables (Abulude, 2001) and varieties of lupin seeds (Trugo et al., 1993). Phytate contents vary considerably depending on the environmental conditions, maturation and processing procedures (Griffiths and Thomas, 1981). Phytate chelates with mineral elements thereby have significant effects on the utilization of the minerals and also interfere with basic residues of proteins. Phytate has been shown to play a role in preventing colorectal carcinoma, hyperchlolesterolaemia and renal calculi (Marounek et al., 2000). Phosphorus assists calcium in many body reactions although it also has its own independent functions (Fleck, 1976). Calcium in conjunction with phosphorus, magnesium, manganese, vitamins A, C and D, chlorine and proteins are all involved in bone formation. Results of Phytate P expressed as percentage of total P were consistent with earlier results on lesser-known leguminous crops seeds (Balogun and Fetuga, 1989). Coefficients of variation of the parameters were not similarly distributed in all it samples.
Results of the phytochemical analyses compared well with literatures (Hassan et al., 2004; Faruq et al., 2004; Olafimihan, 2004). The classes of compounds are known to show curative activity against several pathogens and is therefore not surprising that the plant leaves extracts are used traditionally as an analgesic, antimicrobial and soothing herbs (Hassan et al., 2004). It is documented that presence of saponins can control human cardiovascular disease and reduce blood cholesterol. Tannins may provide protection against microbial degradation of dietary proteins in the rumen (Aletor, 1993).
The results recorded in this research were in total agreement with results obtained by Abulude et al. (2001) for mushrooms. Despite the fact that there is no recommended dietary allowance for potassium and sodium, it is recommended that the intake should be the same to counteract the effect of sodium in raising blood pressure. The leaves may serve as good supplements in the body supply of calcium, magnesium, potassium and sodium. Calcium is important in blood clotting, muscles contraction and in certain enzymes metabolic processes. It is very important that the normal calcium level in the diet should be balanced throughout life. Magnesium is an activator of many enzyme systems and maintains the electrical potential in nerves. Sodium and potassium are required to maintain osmotic balance of the body fluid, the pH of the body, regulate muscle and nerve irritability and control of glucose absorption.
The nutritive values of the leaves were high, since they were rich in mineral elements, efforts to reduce their loss through processing should be ensured. The mineral bioavailability may be low due to high phytate contents. The results obtained for the identified phytochemical compounds showed the therapeutic compositions of the leaves.
ACKNOWLEDGMENTS
The author is grateful to E. Ogundele and A. Adebisi of Horticulture and Landscape Design Department, Federal College of Agriculture, Akure, Nigeria for the identification of the leaves. Also the technical contributions of M. Oladimeji, M. Gabriel and B. Adeyeye of the above College are acknowledged.