Antimicrobial and immunomodulatory properties of extracts of Asparagus setaceous Kunth and Caesalpinia volkensii Harm

Abstract

Infections due to antibiotic resistant microorganisms have become widespread in recent years, and resistance rates among key pathogens have continued to grow at an alarming rate worldwide and the search for novel antimicrobial agents to combat such pathogens have become crucial. It is now an accepted that majority of the antibiotics used in the treatment of these infectious diseases have failed and the ever-increasing resistance to current anti-infective drugs has become a major concern to the medical community. The problem of microbial resistance is still growing and the continued use of antimicrobial drugs in the future remains uncertain. Therefore, actions must be taken to reduce this problem, for example, to control the use of antibiotic, and to continue to develop new novel drugs, either synthetic or natural. The ultimate goal is to offer appropriate and efficient antimicrobial drugs to the patient. For a long period, plants have been a valuable source of natural product for maintaining human health and an impressive number of modern drugs have been isolated from them, many based on their use in traditional medicine. Currently, it is estimated that over 50 percent of all modern clinical drugs are of natural products origin. This study investigated the mode of action of two Kenyan plants namely Asparagus setaceous Kunth and Caesalpinia volkensii Harm. Asparagus setaceous belong to the family Liliaceae while Caesalpinia volkensii belongs to Caesalpinacea. Many medicinal uses of the various parts of plants from these two families have been reported in traditional folklore medicines. These have reportedly been used in the xxx treatment of inflammatory diseases, bronchitis, pneumonia, syphilis and other venereal diseases, malaria and antihelminthic. However, their therapeutic mechanisms remain largely unclear. It is not clear how extracts of these two plants exert their beneficial and therapeutic effects. It is believed that their effects could be direct on the pathogens thus killing them, or to alter and enhance the functioning and activities of immune cells. There was need to investigate and clearly elucidate the mechanisms of actions of these two plants. The aerial part and leaf of A. setaceous and leaf, stem and root of C. volkensii were extracted using polar and non polar solvents. The dichloromethane, hexane, methanol, ethanol and aqueous extracts of A. setaceous root and aerial part and C .volkensii leaf, stem and root were evaluated for their antibacterial and antifungal properties against gram negative (Escherichia coli, Pseudomonas aeruginosa and Streptococcus faecalis) and gram positive (Bacillus subtilis, Staphylococcus aureus) and the fungus Candida albicans. Antibacterial and antifungal activity was tested using the test disc diffusion method. Minimum inhibitory concentration (MIC) of the extracts was also determined. Extracts found to be active were also tested on their ability to affect the growth kinetics of selected pathogens. An assessment to evaluate the ability of the crude extract to affect functioning and activities of immune cells was also carried out. Extracts were administered orally and then the crude extracts were evaluated on their effect on total and differential white xxxi blood cell counts, and ability to reverse cyclophosphamide induced leucopenia in albino rats. The crude extracts were also evaluated on their ability to activate and enhance the function of neutrophils and macrophages. This was done through the neutrophil adherence, Candida and sheep red blood cell phagocytosis and nitroblue