The Use of Essential Oil and Hydrosol Extracted from Cuminum cyminum Seeds for the Control of Meloidogyne incognita and Meloidogyne javanica

Composition Characterization of Cinnamomum osmophloeum Kanehira Hydrosol and Its Enhanced Effects on Erectile Function

Cinnamomum osmophloeum Kanehira (CO) is an endemic species of Taiwan. This study elucidated the composition of CO hydrosol, revealing trans-cinnamaldehyde (65.03%), trans-cinnamyl acetate (7.57%), and coumarin (4.31%) as the main volatile compounds. Seven compounds were identified in the water fraction of hydrosol, including a novel compound, 2-(2-hydroxyphenyl)oxetan-3-ol. This marks the first investigation into high-polarity compounds in hydrosol, extending beyond the volatile components. Notably, two compounds, trans-phenyloxetan-3-ol and cis-phenyloxetan-3-ol, demonstrated significant inhibition activity against phosphodiesterase type five (PDE5), with IC50 values of 4.37 µM and 3.40 µM, respectively, indicating their potential as novel PDE5 inhibitors. Furthermore, CO hydrosol was evaluated against enzymes associated with erectile dysfunction, namely acetylcholinesterase (AChE), angiotensin-I converting enzyme (ACE), and arginase type 2 (ARG2). These findings underscore the potential of CO hydrosol to modulate erectile function through diverse physiological pathways, hinting at its prospects for future development in a beverage or additive with enhanced effects on erectile function.

Nematicidal Potential of Thymol against Meloidogyne javanica (Treub) Chitwood

Root-knot nematodes (RKN; Meloidogyne spp.) are obligatory endoparasites with worldwide distribution which cause severe damage to agricultural crops. The present study aimed to define the nematicidal activity of thymol on different life stages of the root-knot nematode Meloidogyne javanica (Treub) Chitwood, at concentrations of 37.5-1000 μL/L. This study is the first to report the effect of thymol on egg differentiation and also its vapor and sublethal concentration activities. A mortality of greater than 90% of M. javanica second-stage juveniles (J2s) occurred after 96 h of exposure at a concentration of 500 μL/L. At this concentration, thymol inhibited 59.7% of nematode hatching. In addition, the use of thymol at sublethal concentrations reduced the number of females per gram in tomato roots in a pot test, as well as inhibiting egg differentiation. On the contrary, no nematostatic effects were observed in paralysis bioassays. The results presented here indicate that the use of thymol may show its potential as a source of a new sustainable nematicidal product.

Allelopathic Effects of Amomum villosum Lour. Volatiles from Different Organs on Selected Plant Species and Soil Microbiota

Amomum villosum Lour. is a perennial herb of the Zingiberaceae family, which is widely distributed in Xishuangbanna, Yunnan Province in Southwest China. Large amounts of volatile components contained in this plant enter the surrounding atmosphere and soil through volatilization, foliar leaching, root exudation, and residue decomposition. However, the ecological role of these compounds is currently unclear. The aim of this study was to compare the differences in the composition of volatile oils from stems, leaves, and young fruits of A. villosum, identify chemicals that had allelopathic effects, and explore the effects of the oil on the diversity and composition of soil microbiomes. Volatile oils were obtained by steam distillation and characterized by gas chromatography−mass spectrometry, and then were tested for allelopathic activity using seedlings of Lactuca sativa L. and Lolium perenne L. as test species. The results showed that the oils from stems and leaves were rich in monoterpene hydrocarbons, unlike the oxygenated monoterpenes which dominated oils from young fruits. Leaves > stems > young fruits: this was the order of the allelopathic effects of volatile oils from various A. villosum organs. Among the four main chemical components in the oils, only α-pinene, which is abundant in leaves, had a stronger allelopathic action than the crude oils, implying that it might be a potential allelochemical. Experiments on soil microorganisms indicated that 3.0 mg/mL oil had the greatest effect on the structure of the soil fungal community. It can be concluded that A. villosum is capable of releasing allelochemicals which affect the growth of other plant species and the diversity and community structure of soil microorganisms.

Nematicidal Screening of Aqueous Extracts from Plants of the Yucatan Peninsula and Ecotoxicity

Active metabolites from plants are considered safer than synthetic chemicals for the control of plant-parasitic nematodes of the genus Meloidogyne. In the present work, 75 aqueous extracts (AEs) from different vegetative parts of 34 native plant species of the Yucatan Peninsula were evaluated against second-stage juveniles (J2s) of Meloidogyne incognita and M. javanica in microdilution assays. The highest mortality (M) against both Meloidogyne species was produced by the foliar AE from Alseis yucatanensis (M ≥ 94%) and Helicteres baruensis (M ≥ 77%) at 3% w/v after 72 h. Other active AEs at 3% were from the leaves of Croton itzaeus and stems of H. baruensis (M: 87–90%) on M. javanica and the stems of Annona primigenia and the leaves of Morella cerifera on M. incognita (M: 92–97%). The AEs from A. yucatanensis had the lowest LD₅₀ against M. incognita (0.36% w/v), and against M. javanica (3.80% w/v). In an acute ecotoxicity assay of the most promising AEs using non-target earthworms (Eisenia fetida), the AE of A. yucatanensis had slight acute toxicity (LD₅₀: 2.80% w/v), and the rest of the most active AEs were not ecotoxic. These tropical plants are potential candidates for further studies as biorational agents for controlling Meloidogyne species.

Valorization of the Hydrolate Byproduct from the Industrial Extraction of Purple Alium sativum Essential Oil as a Source of Nematicidal Products

The hydrolate byproduct resulting from the industrial essential oil extraction of Spanish purple garlic has been studied against the root-knot nematode Meloidogyne javanica by in vitro and in vivo bioassays. The essential oil, the hydrolate and its organic fraction caused high mortality of juveniles, suppressed egg hatch, and reduced nematode infection and reproduction on tomato plants. The nematicidal compounds of garlic oil, diallyl disulfide and diallyl trisulfide, were the major components of the hydrolate organic fraction. These findings have important implications for the development of new nematode control products based on garlic hydrolate compounds and highlight the recovery of waste from essential oils extraction, promoting a circular economy.

Nematicidal Effects of Volatile Organic Compounds from Microorganisms and Plants on Plant-Parasitic Nematodes

Plant-parasitic nematodes (PPNs) are one of the most destructive plant pathogens worldwide, and controlling them is extremely challenging. Volatile organic compounds (VOCs), which naturally exist in plants and microorganisms, play an important role in the biological control of PPNs and are considered potential substances for the development of commercial nematicides. This paper summarizes the VOCs produced by microorganisms and plants as well as their toxic effects on PPNs. VOCs from 26 microbial strains and 51 plants that are active against nematodes from over the last decade were reviewed. Furthermore, the mechanisms of toxicity of some VOCs against PPNs are also illustrated.