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This research was conducted in Microbiology Laboratory of Godfrey Okoye University to determine the antimicrobial efficacy of aqueous, methanol, ethanol of Pisdium guajava and Citrus x sinensis on the pathogenic Streptococcus mutans and Candida albicans. The Dimethyl sulfoxide was used for dissolving the plant extracts. Pisdium guajava showed antimicrobial activity against C. albicans with the exception of methanol showing no zone of inhibition to any of the isolates. The aqueous and methanol plant extract of Citrus x sinensis showed antimicrobial activity against S. mutans and C. albicans. Citrus x sinensis showed highest inhibition with MIC concentration of 0.256g/ml, 0.064g/ml, 0.032g/ml showed slight growth while concentration 0.016g/ml and 0.008g/ml showed heavy growth, there were scanty growths in the MBC and MFC plates. Phytochemical screening, proximate, chromatographic analyses and the antimicrobial activities of tender stem of Psidium guajava and Citrus x sinesis, were carried out. The phytochemical screening revealed the presence of all metabolites and compounds tested for such as flavonoids, tannins, reducing sugar, terpenes, saponins, anthraquinones and alkaloids.The antimicrobial screening of methanol extract showed activity against the tested organisms. The antimicrobial screening of ethanol and aqueous also showed activity against the tested organisms. The result indicated that the plants had a potential antimicrobial activity and was concentration dependent. The chromatographic analysis of the extracts showed presence of variety of compounds. This therefore, supports the traditional medical use of Psidium guajava and Citrus x sisnesis


Title page                                                                                                                                i

Approval page                                                                                                                         ii

Dedication                                                                                                                              iii

Acknowledgment                                                                                                                   v

Abstract                                                                                                                                  vi

Table of contents                                                                                                                    vii

Lists of figures                                                                                                                        viii

Lists of tables                                                                                                                          xi


1.0 INTRODUTION                                                                                                              1

1.1 AIM AND OBJECTIVES                                                                                              2


2.0 LITERATURE REVIEW                                                                                                            4

2.1 The history of medical plants                                                                                            4

2.2 Guava plant (Psidium guajava)                                                                                        4

2.3 Orange plant (Citrus X sinensis)                                                                                       8

2.4 Test Organisms                                                                                                                 12

2.4.1 Candida albicans                                                                                                           12

2.4.2 Streptococcus mutans                                                                                                     13


3.0 MATERIALS AND METHODS                                                                                    15

3.1 Collections of Plant Materials and Processing                                                                  15

3.2 Qualitative phytochemical screening                                                                                15

3.3 Collection of Microbial Isolates                                                                                        16

3.4 Preparation of media used                                                                                                            16

3.5 Antimicrobial sensitivity assay                                                                                         16

3.6 Determination of Minimum Inhibitory Concentration (MIC)                                          17

3.7 Determination of Minimum Bacteriocidal Concentration (MBC) and Minimum Fungicidal Concentration (MFC)                                                                                     17


4.0 RESULTS                                                                                                                         18


5.0 DISCUSSION                                                                                                                  23


REFERENCES                                                                                                                      25


Table1. Qualitative phytochemical screening of the aqueous, ethanol and methanol extracts of Pisdium guajava plant.                                                                                                   18

Table2. Qualitative phytochemical screening of the aqueous, ethanol and methanol extracts of Citrus x sinensis plant.                                                                                                  18

Table3; Minimum inhibitory Concentration (MIC) broth dilution method; P. guajava and C.sinensis aqueous extract.                                                                                                            20

Table4; Minimum inhibitory Concentration (MIC) broth dilution method; P. guajava and C.sinensis ethanol extract.                                                                                                            20

Table5; Minimum inhibitory Concentration (MIC) broth dilution method; P. guajava and C.sinensis methanol extract.                                                                                                            20

Table 6: Minimum inhibitory Concentrations (MIC) by broth microdilution method of P. guajava and C.sinensis aqueous extract.                                                                                  21

Table 7: Minimum inhibitory Concentrations (MIC) of broth microdilution method of P. guajava and C.sinensis ethanol extract.                                                                                   21

Table 8: Minimum inhibitory Concentration (MIC) by broth microdilution method of P. guajava and C.sinensis methanol extract.                                                                                22


Figure1. Average zones of inhibition (mm) of the crude extracts of P. guajava and C. sinensis on microbial isolates                                                                                                19



Medicinal plants constitute an effective source of both traditional and modern medicine. These plants have been shown to have genuine utility and about 80% of the rural population depends on them as primary health care (Akinyemi, 2000). Plants have been used as sources of remedies for the treatment of many diseases since ancient times and people of all continents especially Africa have this old tradition.Infections caused by pathogenicbacteria and fungi remain an important public health concern particularly in developingcountries because of factors such as: emergence of bacterial and fungal strains that areresistant to most useful antibiotics (Abad et al., 2007; WHO, 2007), HIV/AIDS pandemic(Wagate et al., 2008) and unavailability of vaccine (Assob et al., 2011). Conventionaldrugs are expensive and the western health facilities are also inaccessible to rural people(Matu and Staden, 2003; Wagete et al., 2008).Medicinal plants have been used since time immemorial to treat and prevent humanailments because they have components of therapeutic value (Hassan et al., 2006;Gulluce et al., 2006; Parekh and Chanda, 2007). Domesticated and non-domesticatedanimals in ordinary settings unconsciously treat themselves when sick by eating variousparts of medicinal plants such as leaves, stems, barks and roots (Sindiga et al., 1995).They may also treat their skin conditions by briskly rubbing themselves against suitableplants with curative properties (Sindiga et al., 1995).WHO estimates that up to 80% of the world`s population relies on plants for their primary health care needs (Doughari, 2006; Turker and Usta, 2008; Verma et al., 2011).Such a large population depends on traditional medicine due to factors such as: Increasein resistance to the commonly used antibiotics, high cost and inaccessibility to antibioticsespecially in rural areas. It is however noted that medicinal plants are readily available,they have little side effects and there is extensive local knowledge on herbal medicineamongst the communities (Rojas et al., 2006; Doughari et al., 2008). There are about20,000 plant species used for medicinal purposes (Gulluce et al., 2006). From which atleast 121 chemical substances are extracted (Olila et al., 2007). Some of the known goodsources of pharmacologically active compounds are natural products from fungi andhigher plants (Olila et al., 2001). Many of the effective drugs such as anti-malarial, anticancer, anti-diabetic and antibiotics such as atropine and ergometrine compounds havebeen purified from medicinal plants (Olila et al., 2001; Samie et al., 2005). Medicinal plants are also sources of many active ingredients in the pharmaceutical industries(Maundu and Tengnas, 2005). The popularity of plants medicine is increasing because of their biodegradability, least persistence and less toxic to non-target organisms, economic and easy availability. Guava plant (Psidium guajava) Linn.belonging to family Myrtaceae, a traditionally used plant because of its food and nutrition value. Guava is widely grown in tropical and many areas like India, Bangladesh, Florida, and West Indies. Different parts of the Psidium guajava are reported to be used in folk medicine. Various parts of the plant like root, bark, leaves and fruits are found to possess many pharmacological properties as it is used in the treatment of various disorders. Various evidences depict that the leaves and bark of P. guajava tree possess a long history of medicinal uses.The aqueous extract of guava leaves has been reported to be efficacious in the treatment of various types of gastrointestinal disturbances such as diarrhoea, inhibition of the peristaltic reflex and gastroenteritis. Moreover the whole plant is used as skin tonic and is employed in the treatment of female related disease like dysmenorrhoea, miscarriages, uterine bleeding and premature labour. Recent studies on the pharmacological properties of the bark, fruit and leaves depicts antibacterial, hypoglycaemic, anti-inflammatory, antipyretic, spasmolytic and central nervous system depressant activities. Bark tincture showed fungicidal activity at different concentrations but exhibit only fungistatic property in case of Candida albicans. Leaf extract of psidium guajava also reported for the anti-bacterial activity on staphylococcus aureus due to the protein degrading activity of the leaf extract. The aqueous extract was more potent in inhibiting the growthof E.coli,staphylococcus aureus and Pseudomonas aeroginosathan the organic extracts. The Gram negative bacteria were less susceptible to the effect of crude drugs. The genus Citrus belongs to the family of Rutaceae and is native tropical and subtropical areas in Southeast Asia. The citrus plants are grown worldwide and ranks top in production and trade among the fruit trees. Citrus fruits are richer sources of bioactive compounds having beneficial effect on human health such as vitamin C, carotenoids, flavonoids, limonoids, essential oils, acridone alkaloind, minerals and vitamin B complex. Majority of citrus fruits are eaten fresh such as sweet orange, mandarins, grapefruits etc(metallurgy 2011).



The aim of this study is to determine the antimicrobial efficacy of two medicinal plants (Psidium guajavaand Citrus x sinensis) against two microorganisms (Streptococcus mutans and Candida aldicans).


  1. To determine the Minimum Inhibitory Concentration and Minimum Bactericidal Concentration of Psidium guajava and Citrus x sinensis against the test organisms
  2. To determine the phytochemical properties of Psidium guajava and Citrus x sinensis.




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