1. ANTIBACTERIAL ACTIVITY OF PERSEA AMERICANA
LEAF EXTRACT AGAINST STAPHILACOCOUS MUTANS
Joseck Olukusi Alwala1, Emmanuel Shikanga2, Daniel Buyela Kasabuli2
Wycliffe Wanzala3

2. INTRODUCTION
Persea americana is a large evergreen tree of tropical and sub-tropical regions belonging to the order Laurales in the family Lauraceae.
It is commonly referred to as; Avocado, Alligator Pear (English); Aguacate, Palta (Spanish).
The exact origins of the plant is unknown but it is believed that the plant is native to southern Mexico although it was cultivated from the Rio Grande to central Peru before the arrival of Europeans.
The avocado arrived in South Africa by settlers coming from the West Indies and other Dutch colonies between 1652 and 1700.
Since then, the plant has been cultivated and its fruits are highly valued at national level.

3. INTRODUCTION Cont’d
The export of avocado fruits from Kenya is believed to have started in 1961.
Avocado plant is one of the most important source of nutraceutical and functional foods.
The applications of the plant range from traditional and modern applications in human health to those in ethnoveterinary and Ayurvedic medicines.
Culturally, avocado plants and their fruits and leaves are associated with fortune and fertility in Incas, Aztecs and Mayans.
The seeds of he avocado are used in the treatment of hypertension, inflammatory conditions and diabetes.
They have been found to possess fungicidal, insecticidal, and anti-microbial activities.

4. INTRODUCTION Cont’d
The seeds of he avocado have been found to possess fungicidal, insecticidal, and anti-microbial activities.
Oil from avocado fruit is used as food ingredient in other dishes, as a cooking oil and in cosmetics.
The leaves exhibit analgesic, anti inflammatory, anticancer, antimicrobial, hypoglycaemic, antioxidant, antiviral, hepatoprotective, immunomodulatory, antifungal, antispasmodic, antipyretic, dyslipidemia, and antidiarrheal activities.
Streptococcus mutans is a bacteria responsible for dental caries (tooth decay)
Although extracts on avocado leaves have shown antimicrobial activity on a range of microbes, studies on the anti bacterial activity of leaf extracts against Streptococcus mutans are limited.

5. OBJECTIVES
To determine general composition of hexane, ethyl acetate and methanol extracts from P. americana leaves.
To determine the antibacterial activities of hexane, ethyl acetate and methanol extracts from P. americana leaves against S. mutans.

6. METHODOLOGY
Fresh leaves of P. Americana were collected from Emuhaya Division, Vihiga County, Kenya during the months of June 2015.
P. americana (PAM-005/2015) leaves were identified by botanists in the Department of Botany at Maseno University.
The leaves were air-dried at room temperature for thirty days and ground into a fine powder.
1 kg of the ground leaves was extracted sequentially in triplicate using n- hexane, ethylacetate and methanol (2 liters each).
Each extract was reconstituted in acetone and serially diluted to 0.2; 0.4; 0.6; 0.8 and 1.0 mg.ml-1 using autoclaved distilled water.  
Thin layer chromatography was used to determine the presence of glycosides, alkaloids, steroids, saponins, terpenoids and phenols/tannins.
There is an overlap between the regions where these species occur making it difficult to identify the species based on their locality.

7. METHODOLOGY Cont’d
Streptococcus mutans culture was obtained from Kenya Medical
Research Institute.
Antibacterial tests were conducted by using DISC diffusion assay.
A 50 µℓ volume of S. mutans suspension was streak-innoculated onto the surface of the medium and left undisturbed for 5 h.
Gentamycin and acetone were used as positive and negative controls.
Dilutions of the controls and extract dilutions were applied as 10 µL volumes approximately 3 cm from the centre of the plate in four replicates .
The antifungal activities of the compounds and extracts were determined by measuring the diameters of the inhibition zones after 5 days.

8. RESULTS AND DISCUSSION
Composition of different extracts from avocado leaves
 Sample
Extract
n-hexane
extract
Ethyl acetate
Methanol
Phenols/Tannins + ++ Nd
Stereoids
Alkaloids
Saponins
Terpinoids
Key
+ : present
++ : present in high levels
Nd : Not detected

9. RESULTS AND DISCUSSION Cont’d Concentrations (mg/ml)
Inhibition of Streptococcus mutans by ethyl acetate, methanol and hexane
extracts from Persea americana leaves
Extract
Concentrations (mg/ml)
0.2
0.4
0.6
0.8
1.0
Mean extract
Ethyl acetate extract
6.00
8.20
11.80
15.80
19.00
12.16
Methanol extract
8.00
11.90
15.90
18.70
12.10
Hexane
8.100
12.767
16.00
19.57
12.49
Mean radius
12.156
19.09
C.V.
2.89
LSD P ≤ 0.05
0.463

10. RESULTS AND DISCUSSION Cont’d
All the three extracts exhibited dose dependent activity against Streptococcus mutans.
However, the hexane extract exhibited the highest activity at a concentrations of 0.8 and 1 mg/ml.

11. CONCLUSIONS
The three extracts of P. americana inhibited the growth of S. mutans bacteria.
More studies need to be done in order to isolated the active compounds.

12. ACKNOWLEDGEMENTS
Authors wish to express their gratitude to….

13. THANK YOU!