Reconsidering Hydrosols as Main Products of Aromatic Plants Manufactory: The Lavandin (Lavandula intermedia) Case Study in Tuscany

Abstract

: The present work evaluates for the first time two Lavandin (Lavandula × intermedia Emeric ex Loisel.) aromatic waters obtained from different plant organs, the flowers and the stems. Both extracts were analysed by GC-MS, which indicates semi-quantitative differences between the major metabolites including linalool, 1,8-cineole, camphor, linalyl acetate and 4-terpineol. ¹H-NMR and LC-MS investigation confirmed the presence of these compounds. Moreover, behavioural tests with the food insect pest Tribolium confusum (Coleoptera Tenebrionidae) showed a good repellency for both hydrosols extracts with RD₅₀ values of 3.6 and 3.3 µL cm^-2 for the flowers and stems, respectively; at the higher concentrations, however, the hydrosol extract from the flowers is expected to be more effective than the one from the stems. The effect of the flowers and stems aromatic water of Lavandin on seed germination of Raphanus sativus was also evaluated. Results showed that seed germination was completely inhibited by flowers hydrolate, having a possible application as natural herbicide. The overall experience with these Lavandin extracts indicates the potential of improved hydrolates to become the main distillation products, rather than by-products, of the aromatic plants manufacturing; this stimulates further discussions about the potential positive impacts that such a shift could have in the context of ecopharmacognosy.

Keywords: Lavandula intermedia; fingerprinting analysis; germination inhibitors; hydrolate; hydrosol; insect repellence; lavandin aromatic waters; multifunctional agriculture.

Figure 1

¹H NMR spectra of Lavandin flowers and stems aromatic waters.

Figure 2

Ultra High Performance Liquid Chromatography (UHPLC)-MS (total ion current) chromatogram of Lavandin flower aromatic water, showing oxygenated monoterpenes, tentatively identified among the most abundant components as linaool, 1,8-cineole and borneol/ 4-terpineol.

Figure 3

Mean repellence (%) of Lavandin flowers and stems aromatic waters and of the synthetic repellent MR-08 against Tribolium confusum adults. Bars represent standard error.

Figure 4

Probit model of the repellent effect (Repellence%) of Lavandin flowers (red line) and stems (blue line) hydrosols against Tribolium confusum adults. Dotted lines indicate 95% confidence intervals.

Figure 5

Inhibition of Raphanus sativus seed germination by Lavandin flowers and stems aromatic waters. (A) Raphanus sativus seed + flowers aromatic water; (B) Raphanus sativus seed + stems aromatic water; (C) Raphanus sativus seed + H₂O = control.