Induced production of antifungal naphthoquinones in the pitchers of the carnivorous plant Nepenthes khasiana

Abstract

Nepenthes spp. are carnivorous plants that have developed insect capturing traps, evolved by specific modification of the leaf tips, and are able to utilize insect degradation products as nutritional precursors. A chitin-induced antifungal ability, based on the production and secretion to the trap liquid of droserone and 5-O-methyldroserone, is described here. Such specific secretion uniquely occurred when chitin injection was used as the eliciting agent and probably reflects a certain kind of defence mechanism that has been evolved for protecting the carnivory-based provision of nutritional precursors. The pitcher liquid containing droserone and 5-O-methyldroserone at 3:1 or 4:1 molar ratio, as well as the purified naphthoquinones, exerted an antifungal effect on a wide range of plant and human fungal pathogens. When tested against Candida and Aspergillus spp., the concentrations required for achieving inhibitory and fungicidal effects were significantly lower than those causing cytotoxicity in cells of the human embryonic kidney cell line, 293T. These naturally secreted 1,4-naphthoquinone derivatives, that are assumed to act via semiquinone enhancement of free radical production, may offer a new lead to develop alternative antifungal drugs with reduced selectable pressure for potentially evolved resistance.

Ethnobotanical, Phytochemical, and Pharmacological Properties of Nepenthes Species: A Review

“…A study by Shin et al resulted in the identification and purification of plumbagin from the extract Nepenthes ventricosa x maxima leaves [27]. A liquid from the pitcher of N. khasiana was found to contained 5-0-methyldroserone and droserone [31]. Plumbagin was isolated from the fresh leaves of N. gracilis [32].…”

“…and Candida sp. [31]. The antifungal activity of 3:1 droserone: medroserone mixture tested against C. albicans, Candida glabrata, Candida krusei, and Aspergillus fumigatus showed MICs of 63, 125, 63, and 250 µg/ml, respectively [31].…”

“…[31]. The antifungal activity of 3:1 droserone: medroserone mixture tested against C. albicans, Candida glabrata, Candida krusei, and Aspergillus fumigatus showed MICs of 63, 125, 63, and 250 µg/ml, respectively [31]. The crude hexane extract of Nepenthes ventricosa x maxima leaf showed strong antifungal activity against plant fungal pathogens screened, namely, Alternaria alternata, Aspergillus niger, Bipolaris oryzae, Fusarium oxysporum, Phytophthora capsici, Rhizopus stolonifera var.…”

Why are Aedes mosquitoes rare colonisers of Nepenthes pitcher plants?

“…The exact mode of action of droserones on insect prey is unknown (Raj et al, 2011). These secondary metabolites were also found to be able to inhibit fungal growth as fungal cell walls are made of chitin (Eilenberg et al, 2010).…”

Venus Flytrap (Dionaea muscipula Solander ex Ellis) Contains Powerful Compounds that Prevent and Cure Cancer

“…This molecule gets its name from the plant in which it was discovered, Plumbago zeylanica (59) but is very common and is present in others plants like Limonium axillare or walnut trees ( Juglans sp.) (60–63) but also in other carnivorous plants like N. khasiana, Nepenthes gracilis , or Drosera binata (64, 137, 138). The roots of P. zeylanica were already used for centuries in Indian traditional medicine for their cardiotonic, neuroprotective, and hepatoprotective properties (139).…”