Incubation of Aquilaria subintegra with Microbial Culture Supernatants Enhances Production of Volatile Compounds and Improves Quality of Agarwood Oil

Aromatic components and endophytic fungi during the formation of agarwood in Aquilaria sinensis were induced by exogenous substances

The process of formation of aromatic components for agarwood in Aquilaria sinensis is closely related to endophytic fungi and the result of complex multiple long-term joint interactions with them. However, the interactions between the aromatic components and endophytic fungi remain unclear during the formation of agarwood. In this study, precise mixed solution of hormones, inorganic salts, and fungi was used to induce its formation in A. sinensis, and sample blocks of wood were collected at different times after inoculation. This study showed that the aromatic compounds found in the three treatments of A. sinensis were primarily chromones (31.70-33.65%), terpenes (16.68-27.10%), alkanes (15.99-23.83%), and aromatics (3.13-5.07%). Chromones and terpenes were the primary components that characterized the aroma. The different sampling times had a more pronounced impact on the richness and diversity of endophytic fungal communities in the A. sinensis xylem than the induction treatments. The species annotation of the operational taxonomic units (OTUs) demonstrated that the endophytic fungi were primarily composed of 18 dominant families and 20 dominant genera. A linear regression analysis of the network topology properties with induction time showed that the interactions among the fungal species continued to strengthen, and the network structure tended to become more complex. The terpenes significantly negatively correlated with the Pielou evenness index (p < 0.05), while the chromones significantly positively correlated with the OTUs and Shannon indices.

Production of Volatile Compounds by a Variety of Fungi in Artificially Inoculated and Naturally Infected Aquilaria malaccensis

Aquilaria malaccensis, the resinous agarwood, is highly valued in the perfumery and medicinal industry. The formation of fragrant agarwood resin inconsistently by various fungi is still not clearly understood. The current study investigated the agarwood quality and fungal diversity in artificially inoculated and naturally infected A. malaccensis. The chemical analysis of volatile compounds of agarwood was performed using the Solid Phase Micro Extraction (SPME) method, and the identification of fungi was made through a morphological observation using a light microscope. Gas chromatography analysis revealed the presence of essential compounds related to high-quality agarwood, such as 4-phenyl-2-butanone, β-selinene, α-bulnesene, and agarospirol in both artificially inoculated and naturally infected agarwood but with some differences in the abundance. Further studies on the fungi associated with agarwood volatile compounds formation showed a total of ten fungal group isolates, which were identified based on morphological and molecular studies. The study revealed that agarwood from both artificial and natural sources were naturally infected with Fusarium, Botryosphaeria, Aspergillus, Schizophyllum, Phanerochaete, Lasiodiplodia, Polyporales, and Ceriporia species. This study has offered a potential opportunity to research further the promising development of fungal strains for artificial inducement of high-quality agarwood formation from A. malaccensis trees.

The Combination of Aquilaria sinensis (Lour.) Gilg and Aucklandia costus Falc. Volatile Oils Exerts Antidepressant Effects in a CUMS-Induced Rat Model by Regulating the HPA Axis and Levels of Neurotransmitters

The Aquilaria sinensis (Lour.) Gilg (CX)-Aucklandia costus Falc. (MX) herbal pair is frequently used in traditional Chinese medicine prescriptions for treating depression. The volatile oil from CX and MX has been shown to have good pharmacological activities on the central nervous system, but its curative effect and mechanism in the treatment of depression are unclear. Therefore, the antidepressant effect of the volatile oil from CX-MX (CMVO) was studied in chronic unpredictable mild stress (CUMS) rats. The suppressive effects of CMVO (25, 50, 100 μL/kg) against CUMS-induced depression-like behavior were evaluated using the forced swimming test (FST), open field test (OFT) and sucrose preference test (SPT). The results showed that CMVO exhibited an antidepressant effect, reversed the decreased sugar preference in the SPT and prolongation of immobility time in the FST induced by CUMS, increased the average speed, time to enter the central area, total moving distance, and enhanced the willingness of rats to explore the environment in the OFT. Inhalational administration of CMVO decreased levels of adrenocorticotropic hormone and corticosterone in serum and the expression of corticotropin-releasing hormone mRNA in the hypothalamus, which indicated regulation of over-activation of the hypothalamic-pituitary-adrenal (HPA) axis. In addition, CMVO restored levels of 5-hydroxytryptamine (5-HT), dopamine, norepinephrine and acetylcholine in the hippocampus. The RT-PCR and immunohistochemistry results showed that CMVO up-regulated the expression of 5-HT_1A mRNA. This study demonstrated the antidepressant effect of CMVO in CUMS rats, which was possibly mediated via modulation of monoamine and cholinergic neurotransmitters and regulation of the HPA axis.