An examination of the leaf essential oils of threeEugenia(Myrtaceae) species endemic to New Caledonia

Biocontrol efficacy of cajeput oil against Anopheles stephensi L. mosquito and its effect on non-target species

Chemical insecticides are effective at controlling mosquito populations, but their excessive use can pollute the environment and harm non-target organisms. Mosquitoes can also develop resistance to these chemicals over time, which makes long-term mosquito control efforts challenging. In this study, we assessed the phytochemical, biochemical, and insecticidal properties of the chemical constituents of cajeput oil. Results show that Melaleuca cajuputi essential oil may exhibit mosquito larvicidal properties against Anopheles stephensi larvae (second-fourth instar) at 24 h post-treatment. At 24 h post-exposure, the essential oil resulted in a significant decrease in detoxifying enzymes. All of these findings indicate that cajeput oil infects An. stephensi larvae directly affect the immune system, leading to decreased immune function. Cajeput oil significantly affects the second, third, and fourth instar larvae of An. stephensi, according to the bioassay results. Cajeput oil does not induce toxicity in non-target Eudrilus eugeniae earthworm species, as indicated by a histological study of earthworms. Phytochemical screening and GC-MS analysis of the essential oil revealed the presence of several major phytochemicals that contribute to mosquito larvicidal activity. The importance of cajeput oil as an effective candidate for biological control of the malarial vector An. stephensi is supported by this study.

Chemical diversity of kānuka: Inter- and intraspecific variation of foliage terpenes and flavanones of Kunzea (Myrtaceae) in Aotearoa/New Zealand

Kunzea (Myrtaceae) trees and shrubs, generally called kānuka, grow across most of Aotearoa/New Zealand (NZ). With the exception of K. sinclairii, an offshore island endemic, kānuka had been treated as an Australasian species K. ericoides. However, a 2014 taxonomic revision recognized ten species, all endemic to NZ. Kānuka chemistry is less studied than that of its closest relative in NZ, mānuka (Leptospermum scoparium), which shows very distinct regional foliage chemotypes. We have used a miniaturized method with GC and ¹H NMR to analyze foliage chemistry of voucher specimens from across the geographic ranges of the ten NZ Kunzea species. We found common mono- and sesquiterpenes, with α-pinene dominant in all samples, but only traces of antimicrobial triketones. Two unusual flavanones, with unsubstituted B-rings and known bioactivity against Phytophthora, did distinguish some of the samples. 5,7-Dihydroxy-6,8-dimethyl flavanone was only found at high concentrations in the three K. sinclairii samples in this study's sample set, but this compound has separately been reported in K. robusta samples from a nearby region. Therefore none of the NZ Kunzea species was distinguished by the chemistry analyzed in this study, but there is a possibility of regional flavonoid chemotypes cutting across the species boundaries.

New Caledonia: A ' Hot Spot' for Valuable Chemodiversity: Part 2: Basal Angiosperms and Eudicot Rosids

The flora of New Caledonia encompasses more than 3000 plant species and almost 80% are endemic. New Caledonia is considered as a 'hot spot' for biodiversity. With the current global loss of biodiversity and the fact that several drugs and pesticides become obsolete, there is an urgent need to increase sampling and research on new natural products. In this context, we review the chemical knowledge available on New Caledonian native flora from economical perspectives. We expect that a better knowledge of the economic potential of plant chemistry will encourage the plantation of native plants for the development of a sustainable economy which will participate in the conservation of biodiversity. In the second part of this review, we focus on the results exposed in 60 scientific articles and describe the identification of 225 original compounds from basal angiosperms and eudicot rosids. We discuss the economic potential of plants and molecules from medicinal and industrial perspectives. This review also highlights several plants and groups, such as Amborella sp., Piperaceae, or Phyllanthaceae, that are unexplored in New Caledonia despite their high chemical interest. Those plants are considered to have priority in future chemical investigations.

The Leaf Essential Oil of Eugenia reinwardtiana Growing in Australia

The leaf essential oils of the two chemotypes of Eugenia reinwardtiana (Blume) DC growing in Australia have been investigated. Chemotype 1, isolated in 0.2% yield, w/w, dry weight, contained major amounts of α-pinene (10-26%), limonene (1–15%), β-caryophyllene (0.7–11%), α-humulene (0.9–16%) and bicyclogermacrene (1–23%). The second chemotype, found only on coastal dunes SW of Lockerbie Qld, and isolated in 0.4–0.6% (w/w, dry weight), contained α-pinene (tr −8.5%) β-caryophyllene (12–27%) and α-humulene (1–17%) as the major terpenes. This chemotype also contained the novel aliphatic diketone, 2-butyl-2,4,4-trimethyl-5-methoxycyclohex-5-en-1,3-dione (18–33%), whose structure determination is reported herein.