Genetic Variability and Elite Line Selection for High Essential Oil and Nepetalactone Content in Catmint (<i>Nepeta cataria</i>L.)

Nepeta cataria L., commonly known as catmint or catnip, belongs to the family “Lamiaceae” and is indigenous to Europe and Asia. The essential oil of this species is known for the richness and diversity of nepetalactones (NPL) which are used as mosquito/insect repellents in perfumery and cosmetic industries. Reports on Indian catmint germplasm are very meager and warrants exploration of its commercial potential as a natural, non-toxic source of insect repellents. With this objective, commercial open-pollinated seeds of catmint collected from its native, temperate habitat in Himalayas were introduced in the tropical plains. Subsequent to adaptation to a new zone we were able to isolate nineteen individual plants based on plant growth. Hydrodistillation of the fresh herb yielded essential oil in the range of 0.01% to 0.2%. Gas Chromatography (GC) and GC-Mass Spectrometry (GC-MS) analyses of the oil revealed the dominance of monoterpene hydrocarbon, namely, 4aα,7α,7aα NPL (1) isomer (84%). The other two isomers of nepetalactone, 4aα,7α,7aβ NPL (2) and 4aα,7β,7aα NPL (3) were also present, although in very less amounts (1.0% and 1.6%, respectively). Sesquiterpenes identified were α-humulene (traces), (E)-caryophyllene (0.6%) and caryophyllene oxide (1.7%). We compared the identified Indian catmint chemotype with the other oils from temperate, sub-tropical and tropical locations based on literature search. The Indian chemotype was found to be similar to the oils from Burundi, France, Turkey, UK and USA, mainly due to more accumulation of 4aα,7α,7aα NPL (1) isomer. These oils grouped together in Principal Component Analysis. Breeding lines are presently being developed to improve yield related traits in this plant. Multidisciplinary R&D efforts along with setting up industry related guidelines are required to successfully commercialize catmint cultivation. Several species of Nepeta genus have high nepetalactone content too and their potential as a commercial source of these isomers still needs to be explored.

Evaluation of percutaneous permeation of repellent DEET and sunscreen oxybenzone from emulsion-based formulations in artificial membrane and human skin

Insect repellent DEET and sunscreen ingredient oxybenzone play an essential role in minimizing vector-borne diseases and skin cancers.The purpose of this study was to investigate the effects of emulsion type,addition of thickening agent and droplet size in three emulsion-based lotions on percutaneous permeation of DEET and oxybenzone using in vitro diffusion experiments,in order to minimize overall systemic permeation of the substances.Formulation C(water-in-oil emulsion)significantly increased overall permeation of DEET through human skin(56%)compared to Formulation A(oil-in-water emulsion).Formulation B(oil-in-water emulsion with thickening agent xanthan gum)significantly decreased the size of oil droplet containing DEET(16%),but no effect on oil droplets containing oxybenzone.Adding xanthan gum also increased overall permeation of DEET and oxybenzone(21%and 150%)when compared to Formulation A;presence of both ingredients in Formulation B further increased their permeation(36%and 23%)in comparison to its single counterparts.Overall permeation of oxybenzone through LDPE was significantly higher by 26%-628%than that through human skin;overall permeation of DEET through human skin was significantly higher by 64%-338%than that through LDPE.