Aims: The aim of the study was to verify the antimicrobial activity of commercial essential oils: lavender, tea tree and lemon as the components of a preservative system in oil in water body milks. Methods and Results: The inhibition efficacy of essential oils alone (0·5%), in mixtures (1%) as well as combined with the synthetic preservative 1,3-dimethylol-5,5-dimethylhydantoin and a 3-iodo-2-propynyl butyl carbamate mixture (0·1% and 0·2%) was tested against Staphylococcus aureus ATCC 6538, Pseudomonas aeruginosa ATCC 9027, Candida sp. ŁOCK 0008 and Aspergillus niger ATCC 16404 in compliance with the standards of the European Pharmacopoeia Commission. The in vitro activity of oils determined by an impedimetric method was also compared with their activity in cosmetic preparations. Criterion A for bacteria (reduction in the inoculum by 3 logarithmic units within 7 days with no increase up to the 28th day) and fungi (reduction in the inoculum by 2 logarithmic units within 14 days with no increase up to the 28th day) was fulfilled for cosmetic formulations containing the tested essential oils with 0·2% of the synthetic preservative. The preservative concentration could be decreased to 0·1% (with preserving the same efficacy) in combination with lavender and tea tree oils at a concentration of 0·5% each. Conclusions: In all combinations of essential oils with the synthetic preservative, a synergistic effect of the preservative system components was observed, which made it possible to reduce the usable level of the synthetic preservative up to 8·5 times. Significance and Impact of the Study: To develop an effective preservative system in cosmetics in which a synthetic chemical preservative is replaced by natural essential oils.

The chemical composition of essential oils and hydrolate from dried lavender flowers (Lavandula angustifolia) was determined. Organic compounds were isolated from the hydrolate by the liquid–liquid (LLE) method. Optimal conditions for LLE (pentane, five extraction cycles, 40 mL, salting out [5% NaCl]) were determined by the Taguchi method. As many as forty-seven compounds were identified both in the essential oil (Oe) and in the essential oil isolated during the preparation of hydrolate (OeH), representing 94.9% of the content of Oe and 95.7% of OeH. The main compounds in OeH and Oe are: linalool (24.6% and 24.9%, respectively), linalyl acetate (14.4% and 18.0%, respectively) and borneol (6.2% and 6.3%, respectively). The most abundant compounds are oxygenated derivatives of monoterpenes (74.3% Oe, 73.4% OeH), including monoterpene alcohols (40.5% Oe, 38.0% OeH). In the hydrolate (H), twenty-four compounds, representing 83.8% of its composition, were identified. The main ingredients are: linalool (26.5%) and borneol (9.0%). Also here, oxygenated derivatives of monoterpenes predominate (78.1%), consisting mainly of alcohol monoterpenes (50.7%). In the hydrolate, the presence of acetate linalyl, monoterpenes, or sesquiterpenes was not found. Quantitative analysis of Oe, OeH and H was conducted for selected chemical compounds.

The study was undertaken to verify the antimicrobial activity of Lavandula angustifolia hydrosols in moisturizing body gels. The inhibition efficacy of four lavender hydrosols (obtained from fresh or dry herbs or flowers) was tested against Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 1627, Candida sp. ŁOCK 0008 and Aspergillus niger ATCC 16404 in compliance with the standards of the European Pharmacopoeia Commission. Although the tested hydrosols did not express any remarkable antimicrobial action when tested via the macrodilution method, they show preservative activity in cosmetic preparations. Criterion A for fungi was fulfilled for the cosmetic formulation containing dried flower hydrosol (reduction of the inoculum by two logarithmic units within 14 days with no increase up to the 28th day) and Criterion B for bacteria E. coli and Staph. aureus (reduction of the inoculum by three logarithmic units within 14 days with no increase up to the 28th day). The fresh herb lavender hydrosol in the cosmetic formulation was regarded as the second one effectively satisfying Criterion B for bacteria, but its activity against fungi was below the acceptance value set out in the official regulations. Lavender hydrosols used as a replacement for water phase in cosmetics may contribute to maintaining microbiological stability of cosmetic formulations. Significance and Impact of the Study The presented research proved antimicrobial activity of hydrosols obtained from fresh or dried Lavandula angustifolia herbs or flowers in moisturizing body gel. The study shows the usefulness of lavender hydrosols as a natural, ecologically friendly component of cosmetics with potential preservative activity in formulations. Hydrosols are commonly regarded as waste in the production of essential oils. The use of lavender hydrosols in the cosmetic industry as a replacement for water phase in cosmetics may not only result in expenses reduction for chemical stabilizers and preservatives but also in substantial decrease in sewage disposal.