Enhancing the Accumulation of Rosavins in Rhodiola rosea L. Plants Grown In Vitro by Precursor Feeding

Rhodiola rosea produces nearly 150 bioactive compounds. Cinnamyl alcohol glycosides (CAGs) are among the most important secondary metabolites which are specific to this plant species, exhibiting adaptogenic properties along with salidroside. However, raw material supplies for the pharmaceutical industry are hindered by limited access to the plant material. The species is endangered and protected in many areas: cultivation is long and ineffective. Precursor feeding has been found to be an effective strategy for improving the production of secondary metabolites in various plant tissues cultures, including in Rhodiola species. In this study, whole R. rosea plants grown in vitro were subjected to three different precursor treatments, including with trans-cinnamic acid, cinnamaldehyde and cinnamyl alcohol at 2 mM concentrations. The different treatments affected the secondary metabolite production differently. Trans-cinnamic acid did not affect the synthesis significantly, which contradicts earlier studies with cell suspensions. On the other hand, cinnamyl alcohol and cinnamaldehyde were beneficial, improving the production rate of rosin and rosavin by 13.8- and 6.9-fold, and 92.7- and 8.0-fold, respectively. The significant improvement in CAG accumulation due to cinnamaldehyde treatment was unexpected based on previous studies. In addition, cinnamaldehyde triggered the production of rosarin, which the other two treatments failed to do. The study presents the beneficial application of precursors to whole plants grown in vitro.

Headspace Volatiles and Endogenous Extracts of Prunus mume Cultivars with Different Aroma Types

Prunus mume is a traditional ornamental plant, which owed a unique floral scent. However, the diversity of the floral scent in P. mume cultivars with different aroma types was not identified. In this study, the floral scent of eight P. mume cultivars was studied using headspace solid-phase microextraction (HS-SPME) and organic solvent extraction (OSE), combined with gas chromatography-mass spectrometry (GC-MS). In total, 66 headspace volatiles and 74 endogenous extracts were putatively identified, of which phenylpropanoids/benzenoids were the main volatile organic compounds categories. As a result of GC-MS analysis, benzyl acetate (1.55–61.26%), eugenol (0.87–6.03%), benzaldehyde (5.34–46.46%), benzyl alcohol (5.13–57.13%), chavicol (0–5.46%), and cinnamyl alcohol (0–6.49%) were considered to be the main components in most varieties. However, the volatilization rate of these main components was different. Based on the variable importance in projection (VIP) values in the orthogonal partial least-squares discriminate analysis (OPLS-DA), differential components of four aroma types were identified as biomarkers, and 10 volatile and 12 endogenous biomarkers were screened out, respectively. The odor activity value (OAV) revealed that several biomarkers, including (Z)-2-hexen-1-ol, pentyl acetate, (E)-cinnamaldehyde, methyl salicylate, cinnamyl alcohol, and benzoyl cyanide, contributed greatly to the strong-scented, fresh-scented, sweet-scented, and light-scented types of P. mume cultivars. This study provided a theoretical basis for the floral scent evaluation and breeding of P. mume cultivars.

Selective Oxidation of Cinnamyl Alcohol to Cinnamaldehyde over Functionalized Multi-Walled Carbon Nanotubes Supported Silver-Cobalt Nanoparticles

The selective oxidation of alcohols to aldehydes has attracted a lot of attention because of its potential use in agrochemicals, fragrances, and fine chemicals. However, due to homogenous catalysis, low yield, low selectivity, and hazardous oxidants, traditional approaches have lost their efficiency. The co-precipitation method was used to synthesize the silver-cobalt bimetallic catalyst supported on functionalized multi-walled carbon nanotubes (Ag-Co/S). Brunauer Emmet Teller (BET), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and X-ray diffraction (XRD) were used to characterize the catalyst. For the oxidation of cinnamyl alcohol (CA) with O2 as an oxidant, the catalyst’s selectivity and activity were investigated. The impacts of several parameters on catalyst’s selectivity and activity, such as time, temperature, solvents, catalyst dosage, and stirring speed, were comprehensively studied. The results revealed that in the presence of Ag-Co/S as a catalyst, O2 could be employed as an effective oxidant for the catalytic oxidation of cinnamyl alcohol to cinnamaldehyde (CD) with 99% selectivity and 90% conversion. In terms of cost effectiveness, catalytic activity, selectivity, and recyclability, Ag-Co/S outperforms the competition. As a result, under the green chemistry methodology, it can be utilized as an effective catalyst for the conversion of CA to CD.