Duangkhae Maneenuan

Investigation of inclusion complexes of citronella oil, citronellal and citronellol with β-cyclodextrin for mosquito repellent

The aim of this study was to prepare the inclusion complexes of citronella oil, citronellal or citronellol with β-cyclodextrin and evaluate their physicochemical properties using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). A kneading method was employed to prepare the inclusion complexes and weight ratios of each of the active substance to β-cyclodextrin were 1:1 (1:1 CPX) and 1:2 (1:2 CPX). For comparison purposes, physical mixtures of these active compounds and β-cyclodextrin were also prepared and investigated. Unlike the physical mixtures, the SEM technique revealed drastic changes in the shapes and morphologies of the particles for the inclusion complexes. Furthermore, the FTIR and DSC results seemed to reveal some interactions between the active substance and β-cyclodextrin. The o/w lotions, which contained 10% w/w citronella oil (normal citronella oil; 1:1 CPX or 1:2 CPX), were formulated using Cremophors as emulsifiers. With modified Franz diffusion cell and synthetic membrane, the release rates of citronella oil from the lotions containing the inclusion complexes were significantly lower than that from the prepared lotion containing normal citronella oil. The mosquito (Aedes aegypti) repellent efficacy of the lotions containing citronella oil, citronellal or citronellol (both normal and inclusion complexes) was further evaluated by human-bait technique. The highest mosquito repellent activity was observed in the formulation which contained citronella oil–β-cyclodextrin inclusion complex at weight ratio of 1:1.

Effects of glucam P-20, vanillin, and fixolide on mosquito repellency of citronella oil lotions.

ABSTRACT The objective of this study was to investigate the effects of three fragrance fixatives, Glucam P-20, Vanillin, and Fixolide, on the mosquito repellent property of citronella oil lotions. In the current study, two formulae (A and B) of oil-in-water citronella oil lotions were formulated using different ingredients (emulsifiers [Cremophors or Emulwax], stiffening agents, and emollients). Citronella oil was used at 10% wt:wt. The weight ratios tested between citronella oil and each fixative were 1:0.25, 1:0.5, and 1:1. Overall, 20 formulations, including one with no fixatives for both A and B, were produced, A1–A10 and B1–B10. The repellent activities of these 20 lotions against Aedes aegypti (L.) were tested using a human-bait technique. The types and concentrations of fixatives as well as the compositions of the formulations did affect the protection time of the citronella oil lotions. The lotion containing Emulwax and 5% vanillin (B6) was the most effective repellent. It provided the longest protection time of 4.8 h, which exceeded the minimum requirement of 2 h set by the National Institute of Health, Thailand. The shortest protection time (1 h) was observed in the lotion containing Emulwax and 2.5% Glucam P-20 (B2). It could be concluded that the tested fixatives affected the repellent activity of the citronella oil lotions.

In vitro release, skin permeation and retention of benzophenone-3 from microemulsions (o/w and w/o)

The major aim of this work was to investigate the effect of microemulsion type on the in vitro release, skin permeation and skin retention of benzophenone-3 microemulsions. Based on the microemulsion regions of ternary phase diagrams, two types of microemulsions were formulated. This included w/o microemulsions containing Tween 20 or Tween 80 (surfactant), Eutanol G (oil) and water and o/w microemulsions containing additional component, a 1:1 mixture of surfactant and cosurfactant (isopropyl alcohol). Overall, four microemulsion formulations at ratio of 18:72:10 (oil:surfactant or mixtures of surfactant and cosurfactant:water) were prepared. Each blank microemulsion was incorporated with 5 % w/w benzophenone-3, a sunscreen. Physicochemical property and stability (both physical and chemical) of the prepared formulations were acceptable. All microemulsions showed negative zeta potential values. The mean droplet sizes of the w/o type (14–54 nm) were much smaller than the o/w type (136–210 nm). The release kinetics of all formulations followed zero order. Unlike the skin retention, microemulsion type affected the release characteristics and skin permeation of benzophenone-3. The o/w microemulsions showed markedly high release rates and skin permeation rates. The w/o microemulsions providing low transdermal fluxes may be promising for topical delivery of the sunscreen.