Project Materials

CHARACTERIZATION, INSECTICIDAL AND MOSQUITO REPELLENCY PROPERTIES OF ESSENTIAL OILS FROM HYPTIS SUAVEOLENS LEAVES

ABSTRACT

Essential oils were extracted from Hyptis suaveolens leaves via hydro-distillation, and the mosquitocidal impact was determined using an experiment designed specifically for this study. The essential oils’ effect on mosquito larvae (larvicidal), repellent effect, and physicochemical qualities were investigated using established procedures. The essential oils were analysed using gas chromatography-mass spectrometry (GCMS) and Fourier Transform Infrared (FTIR). The percentage yield of the essential oils was 0.05, and for the larvicidal activity, dose dependent mortality of the larvae was observed; there was a low mortality rate at lower dosages that were not significantly different from each other, e.g., 6.25 and 12.50ppm had the same LC50 and LC90 of 25.21 and 302.67, 25ppm had LC50 and LC90 of 9.58 and 352.46, and 50-1000ppm had LC50 and LC90 of 0.55 and 0.85, respectively. It was discovered that the volume of air entering and exiting the cage influences the rate at which mosquitoes are repelled. In a group of mosquitoes kept in a cage with all sides open (ASO), 65% of the mosquitoes were repelled within 30 minutes, whereas 73% and 85% of the mosquitoes were repelled within the same time frame. In a second experiment, mosquitoes were completely repelled from the surface of rats with shaved skin when essential oil was administered. The essential oil also showed dose-dependent mosquitocidal action, with LC50 and LC90 values of 6 and 21 ppm, respectively. The essential oil’s physicochemical qualities are as follows: iodine value 23.59+0.12g/100g, saponification 100.18+0.8mgKOH/g, peroxide value 40.00+0.02meq/kg, acid value 3.37+0.01mgKOH/g, ester value 34.30+1.00mg/g, and free fatty acids 0.15+0.57%. Terpenes were discovered to be the predominant organic compound present in the essential oil using GC-MS analysis, which was validated by FTIR with the O=C-O-C stretch functional group suggesting the presence of terpenes. Thus, the presence of terpenes in Hyptis suaveolens essential oil could have contributed to its insecticidal and mosquitocidal capabilities.

Chapter one

INTRODUCTION

1.1 Background of the study

Plants have always provided food and medicine to humans since the dawn of time. Their nutritional and therapeutic properties have been related to the phytochemicals and other chemical elements found in them.

Despite its importance, it has been stated that only around 300 of the world’s 250,000 to 500,000 plant species are used in the food, pharmaceutical, cosmetic, and perfume sectors. Traditionally used medicinal plants provide a wide range of chemicals with proven therapeutic effects (Umedum et al. 2014).

Medicinal plants are used in traditional medicine to treat a number of illnesses. In recent decades, the area of herbal medicine has grown at an exponential rate. For generations, natural products have been used to produce medications (Dinet al., 2011).

Traditional medicines (plant sources) have been used for thousands of years to treat malaria and are the source of two major classes of current antimalarial pharmaceuticals (artemisinin and quinine derivatives) (Kazembe et al., 2012).

Repellents are compounds applied to the skin to prevent insects from biting it (Traoré-Coulibaly et al., 2013). An insect repellent is a chemical that encourages an organism to move away from an odour source; insects detect volatile repellents by smell (Luts et al. 2014).

Essential oils are volatile natural complex secondary metabolites with a strong aroma and a lower density than water (Arun et al. 2009).