Encapsulation of nutraceutical monoterpenes in beta-cyclodextrin and modified starch

ABSTRACT:  The encapsulation of thymol and geraniol in β -cyclodextrin (β-CD) and modified starch (MS) by spray- and freeze-drying was studied. The formation of thymol/β-CD and geraniol/β-CD inclusion complexes was confirmed by differential scanning calorimetry (DSC). Oxidative DSC revealed that the monoterpenes enclosed in the β-CD cavity were protected against oxidation, remaining intact in temperatures at which free monoterpenes were oxidized. Phase solubility studies showed that the inclusion complexes of thymol and geraniol with β-CD are more soluble in water than the free molecules themselves. Furthermore, in order to evaluate the fraction of monoterpenes that can be released from their complexes with MS in aqueous media, a series of release experiments were conducted.     

Field response of predatorRhizophagus grandis to prey frass and synthetic attractants

A lure based on the proportional composition of monoterpenes inD. micans larval frass and deployed in Theysohn slot traps was highly attractive toR. grandis released in the field. The relative response to frass and lure was consistent over a range of doses, and behavior close to traps baited with either lure or frass appeared to be similar. The monoterpenes, formulated with antioxidant, appear to be stable over several weeks when released from proprietary reservoir and wick “air fresheners.” The lure may be of value in monitoring predator populations.     

Effects of some natural volatile compounds on the pathogenic fungiAlternaria alternata andBotrytis cinerea

A bioassay system was developed to test the effects of volatile compounds on the growth of hyphae from germinating fungal spores. Volatiles from crushed tomato leaves inhibited hyphal growth of two fungal pathogens,Alternaria alternata andBotrytis cinerea. Aldehydes, including C₆ and C₉ compounds formed by the lipoxygenase enzyme pathway upon wounding leaves, inhibited growth of both fungal species. Terpene hydrocarbons, 2-carene and limonene, had no significant effect on hyphal growth. The quantities of volatile compounds in the vapor phase of the bioassay system were measured by direct headspace sampling and GC analysis.     

Defensive secretions of new zealand tenebrionids:

The defensive secretions of four species of the genusArtystona endemic to New Zealand differ from those of other tenebrionids in that they contain -pinene and limonene, as well as the more characteristic quinones and alkenes. Adults and larvae ofA. obscura, A. erichsoni, A. rugiceps, andArtystona sp. feed on the lichenParmotrema reticulatum (Taylor), but the terpenes are not sequestered from it. The defensive secretions of the four species show some interspecific variation.     

Multivariate discrimination of host use by dwarf mistletoeArceuthobium vaginatum subsp.cryptopodum: Inter- and intraspecific comparisons

The parasitic dwarf mistletoeArceuthobium vaginatum attacksPinus ponderosa as its primary host andP. contorta as an occasional host. Within ponderosa pine stands there is also differential parasitism among individual trees. We compared biochemical features of phloem and xylem oleoresin between infected individuals of the two pine species (N=15 for each species) and also between infected (N=30) and nearby uninfected (N=30) ponderosa pine conspecifics. There were significant differences in chemical features, both at the interspecific (P. ponderosa vs.P. contorta) and intraspecific (P. ponderosa) levels. Discriminant function analysis based on chemical features of phloem correctly classified all trees used in the analysis as eitherP. ponderosa orP. contorta, and 95% of all ponderosa pine trees as either parasitized or nonparasitized. Monoterpene composition of oleoresin was distinct between species, and differences between parasitized and nonparasitizedP. ponderosa were also significant. Many of the observed chemical differences are probably constitutive, although levels of nonstructural carbohydrates and -pinene may change in response to dwarf mistletoe infection. Biochemical differences at the intraspecific level were distinct from interspecific differences. Patterns of differential attack can have genetic consequences upon both the parasite and its hosts, and, in the process, may contribute to the evolution of host races of the parasite and to the evolution of host resistance within ponderosa pine.     

Technique for using microencapsulated terpenes in lepidopteran artificial diets

We have developed and tested a technique to microencapsulate terpene compounds by forming gelatin-walled microcapsules around the terpene essential oils. Eight terpenes that are common constituents of Douglas fir (Pseudotsuga menziesii) oleoresin were encapsulated, including five monoterpenes (-pinene,-pinene, camphene, myrcene, and limonene) and three oxygenated monoterpenes (bornyl acetate, linalool, and-citronellol). The encapsulated terpenes were mixed into artificial diets to determine the effects they had on western spruce budworm (Choristoneura occidentalis) survival and reproduction, using a three-generation bioassay. We describe the technique and present data from preliminary bioassays with seven of the terpenes to demonstrate thatC. occidentalis larvae would consume diets fortified with microencapsulated terpenes. The technique is useful because it helps to reduce the rate at which terpenes volatilize from the diets and it packages the terpenes in a manner more closely resembling the way they are present in the resin canals of plant foliage. Many scientists investigating the biological importance of terpenes in mediating plant-herbivore interactions may find that microencapsulated terpenes are useful in both laboratory diet studies and field and greenhouse experiments with plant material.     

Altered Constitutive and Inducible Phloem Monoterpenes Following Natural Defoliation of Jack Pine: Implications to Host Mediated Interguild Interactions and Plant Defense Theories

Foliar feeding by the jack pine budworm Choristoneura pinus pinus altered the constitutive and induced monoterpene content and composition of Pinus banksiana phloem. In constitutive phloem tissue the ratios of -pinene to -pinene decreased with defoliation intensity. Biochemical responses to simulated bark beetle attack were also influenced by defoliation intensity. Total monoterpene concentrations were always higher in induced than constitutive tissue, but the extent and rate of monoterpene accumulation, and also proportionate changes in monoterpenes during induction, varied with defoliation intensity. Quantitative and compositional changes in response to simulated bark beetle attack were also affected by host seasonal phenology and time since defoliation. There was a positive relationship between myrcene concentration and arrival by the bark beetle Ips grandicollis. Bark beetle arrival rates were more strongly associated with the chemical composition of constitutive than reaction phloem chemistry. However, chemical changes during induced host responses were also associated with beetle behavior. The ratio of -pinene to -pinene during the first three days of induction was consistently associated with both defoliation by C. pinus pinus and susceptibility to I. grandicollis. These results show that direct injury to one plant tissue, foliage, cannot only cause chemical changes in another tissue, phloem, but such changes can be greater in the tissue not directly affected. The influence of defoliation intensity on monoterpene accumulation suggests a link between production and allocation of carbon within P. banksiana. The relationship between defoliation level and induced monoterpene concentrations was either parabolic or inverse, depending on the interval following defoliation. Likewise, the relationship between plant growth and defoliation intensity varied with the length of time following defoliation. Thus, plant defense theories can be improved by incorporating the length of time during which the effects of a stress are exerted.     

Changes in the Composition of Phospholipid Fatty Acids and Sterols of Maize Root in Response to Monoterpenes

Terpenes are thought to be important in plant–plant interactions because of their phytotoxic action on seed germination and growth. Herein, the effects of five volatile monoterpenes on root sterols and phospholipid fatty acid (PLFA) composition have been studied during maize seedling germination. The investigated monoterpenes (camphor, 1–8 cineole, geraniol, menthol, and thymol) were applied at their respective IC₈₀ (concentration causing 80% inhibition). They quantitatively affected free sterols and PLFA composition, thus producing an increase in the percentage of unsaturated PLFAs, stigmasterol of the free sterol fraction, and saturated steryl ester fatty acids. Alcoholic and nonalcoholic monoterpenes appeared to have different modes of action. The former affected unsaturated fatty acid and stigmasterol to a greater extent, and accordingly they could interfere in seedling growth by changes in the membrane lipids.     

Effects of nitrogen and Douglas-fir allelochemicals on development of the gypsy moth,Lymantria dispar

Two experiments were conducted to examine the influence of foliar nitrogen, terpenes, and phenolics of Douglas-fir on the development of gypsy moth larvae. In the first experiment, foliar concentrations of nitrogen and allelochemicals were manipulated by fertilizing 3-year-old potted seedlings with 0 or 200 ppm nitrogen. Concentrations of foliar nitrogen (0.33–2.38%) were negatively correlated with the phenolics (15.8–24.4 mg/g). Sixth-instar larvae previously reared on current-year Douglas-fir needles were allowed to feed on these seedlings. Pupal weights (312.8–995.6 mg) were positively correlated with levels of foliar nitrogen, negatively correlated with amounts of foliar phenolics, and uncorrelated with terpene concentrations. In the second experiment, terpene and phenolic extracts from Douglas-fir foliage were incorporated at natural levels into artificial diets with high and low levels of protein nitrogen. Neonate larvae grew faster and were larger on the high nitrogen control diet (4.1–4.5%), however, fourth instars performed better on the control diet with low nitrogen levels (2.5–2.7%). Foliar terpenes incorporated into diet had little effect on neonate fitness, but may induce subtle physiological changes in later instar larvae. Phenolics, alone or in combination with terpenes, excessively suppressed growth and survival, with no individuals living through the fourth instar, regardless of the nitrogen level. Incorporating foliar phenolic extracts into artificial diet caused unnatural levels of toxicity and failed to clarify the effects of Douglas-fir phenolics on gypsy moth fitness. Foliar nitrogen is a key factor influencing gypsy moth development on Douglas fir, but may be mitigated to some degree by phenolics.