Aroma Components in Horticultural Crops: Chemical Diversity and Usage of Metabolic Engineering for Industrial Applications

Revealing the key aromatic compounds in Malus 'Lollipop' flowers by transcriptome and metabolome

The ornamental crabapple Malus (M.) 'Lollipop' is renowned for its compact growth and fragrant flowers. This study aims to elucidate the biosynthesis molecular mechanism of volatile organic compounds (VOCs) across four developmental stages of the M. 'Lollipop' flowers using metabolomics and transcriptomics analyses. Gas chromatography-mass spectrometry (GC-MS) identified 29 VOCs (aliphatic derivatives, benzenes, and alkanes) in M. 'Lollipop' flowers. Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA) analysis highlights 14 key differential aromatic compounds (VIP ≥ 1), featuring (Z)-3-hexen-1-yl acetate in stage 1, methyl benzoate in stage 2, benzyl alcohol and linalool in stage 3, and camphene and (Z)-3-hexen-1-ol in stage 4. (Z)-3-hexen-1-yl acetate was identified as a co-primary constituent in the four flowering stages, designated as a key and floral contributing metabolite (variable importance in projection (VIP) ≥ 1& odor activity value (OAV) ≥ 1). RNA sequencing revealed key genes including CAT, DXS, MVD, HMGCR, FDPS, and TPSc in camphene and linalool synthesis, aroA, ADT, PDT, PAL, BEBT1, SDR, 4CL, CNL, and BALDH for benzyl alcohol, benzaldehyde, and methyl benzoate production. And PLA2G, SPLA2, TGL4, LOX2S and ADH1 in (Z)-3-hexen-1-yl acetate and (Z)-3-hexen-1-ol synthesis. 24 transcription factors (TFs) were predicted to be closely linked to genes involved in VOC synthesis. The findings above deepen our comprehension of the floral scent in crabapple, laying a foundation for further investigations into their functions and potential industrial applications.

Comprehensive review of sweetpotato flavor compounds: Opportunities for developing consumer-preferred varieties

Flavor contributes significantly to consumer preferences of cooked sweetpotato. Sugars largely drive the sweet taste, while the volatile organic compounds (VOCs), mainly classified as alcohols, aldehydes, ketones, and terpenes, provide characteristic aromas and influence the overall perception of flavor. In this paper, we review sweetpotato VOCs identified in the literature from 1980 to 2024 and discuss the efforts to understand how these compounds influence sensory perception and consumer preferences. Over 400 VOCs have been identified in cooked sweetpotato with 76 known to be aroma-active. Most of these aroma-active compounds are generated from Maillard reactions, Strecker, lipid and carotenoid degradation, or thermal release of terpenes from glycosidic bonds during cooking. Suggested mechanisms of formation of these aroma-active compounds are described. However, specific VOCs that are responsible for different aromas and flavors in cooked sweetpotatoes are yet to be fully characterized. There are significant opportunities to further identify the key predictors of aroma and flavor attributes in sweetpotato, which can be used to enhance the quality of existing varieties and develop new ones using a wide range of genetic tools. This review summarizes 44 years of research aimed at identifying key aroma compounds in cooked sweetpotato and provides a roadmap for future studies to guide breeders in developing high-quality, consumer-preferred varieties.

The Psychophysiological Relaxation Effects of Essential Oil Combined with Still-Life Painting Activities on Older Adults in Taiwan During the COVID-19 Pandemic

Although the COVID-19 pandemic affected all types of people, older adults were disproportionately affected. Therefore, we developed an indoor program inspired by art and natural elements (plant essential oils [EOs]) intended to have a relaxing effect akin to a forest atmosphere to enhance psychophysiological health during this period. Thirty Taiwanese older adults (range, 59-79 years) participated in the study. We combined an art activity (still-life painting of vegetables) with the inhalation of Pseudotsuga menziesii and Lavandula angustifolia EOs during a 100-minute experiment. The study showed that physiological measures (heart rate, normalized low-frequency heart variability, the ratio of low- to high-frequency heart variability, high-beta waves, and gamma waves) decreased during the experiment; correspondingly, increased standard deviation of normal-to-normal intervals, normalized high-frequency heart variability, and high-alpha waves were observed, indicating relaxed physiological state. Subjective psychological assessments using the State-Trait Anxiety Inventory-State showed lower posttest scores, further supporting the relaxation effects. The psychophysiological data from this study provide important scientific evidence for the physical and mental health benefits of indoor nature-based activity programs for older adults, thereby improving their quality of life.

Plant Volatile Organic Compounds: Revealing the Hidden Interactions

Volatile organic compounds (VOCs), classified as secondary or specialized metabolites, are essential for plant health [...].

Volatile profile and potential predictors of astringency loss in fresh, whole 'Rama Forte' persimmon fruit

Volatile profile of fresh, whole 'Rama Forte' persimmons treated with CO2 or ethanol (EtOH) vapor for astringency removal, and the relationship of the main volatile organic compounds (VOCs) with the loss of astringency were investigated. Persimmons were harvested at the commercial maturity stage and treated with 70 % CO2, 18 h, or 1.70 mL kg-1 EtOH, 6 h. Headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry allowed the tentative identification of 34 VOCs, 15 of them are reported for the first time on persimmons. Ethanol was the relevant compound common to CO2 and EtOH-treated samples in the first days after treatment, while acetoin, hexanal, and trans-2-hexenal ((E)-hex-2-enal) were the relevant VOCs in samples from the last days after treatment. As the astringency reached its lowest levels, some of the main VOCs had their relative intensity increased. Pentadecanal, ethyl acetate, acetoin, and ethanol may be potential predictors of astringency loss in fresh, whole 'Rama Forte' persimmons.

Review of polysaccharides from Citrus medica L. var. sarcodactylis. (Fingered citron): Their extraction, purification, structural characteristics, bioactivity and potential applications

Citrus medica L. var. sarcodactylis. (Fingered citron), commonly known as Buddha's hand, is a revered member of the Citrus genus belonging to the Rutaceae family with a long history in China. Fingered citron is known for its multifaceted utility as traditional herbal medicine, functional food and ornamental plant. Fingered citron polysaccharides (FCPs) are the key bioactive components of Citrus medica L. var. sarcodactylis, garnering global attention for their potential medicinal and culinary benefits. Various extraction methods like solvent extraction, ultrasound or microwave-assisted extraction have been used to obtain FCPs. Nonetheless, the structural characteristics of FCPs remain incompletely understood, necessitating further research and elucidation of the potential structure-activity relationship via the combined use of various advanced analytical techniques. Furthermore, FCPs exhibit diverse bioactivities, such as antioxidant activity, immunomodulatory effect, anti-inflammatory effect and gut microbiota regulatory activity, among others, positioning them as viable candidates for the therapeutic and health-promoting applications. Consequently, this review seeks to offer a comprehensive overview of FCPs, covering their extraction, purification, structural features, biological activities, and potential applications, underscoring the significant promise of FCPs as valuable natural compounds with multiple bioactive properties, advocating for their expanded utilization and integration into industry and therapeutics.

Antioxidant content following fermentation of lemongrass for herbal beverage development

Consumers have increasingly favoured fermented drinks due to their high content of probiotic secondary metabolites. These beverages are believed to possess the capacity to safeguard against non-communicable ailments such as coronary heart disease, cancer, diabetes, antimicrobial infections, and other dietary-related disorders. Lemongrass (Cymbopogon citratus) is a commonly used botanical ingredient in therapeutic tea production. It is renowned for its highly valuable essential oil, which has significant commercial demand. This study examines the functional content and antioxidant effects of fermented beverages derived from lemongrass. We employed the yeast Saccharomyces cerevisiae to carry out the fermentation process on the lemongrass compositions, extending the duration from t = 24 to t = 96 h. We used non-fermented samples as control. This investigation identified numerous active biomolecules and polyphenols in the fermented samples, including flavonoids, tannins, cardiac glycosides, coumarins, terpenoids, steroids, saponins, and reducing sugars. After t = 24 h fermentation, the radical-scavenging activity reached its maximum level of 89.1%, and the antioxidant content reached 13.06 µg/ml, which is equivalent to the amount of ascorbic acid. After t = 36 h fermentation, the total phenolic content reached a concentration of 237.19 µg/ml, while the flavonoid content reached its peak at 55.21 µg/ml after t = 72 h fermentation. Lemongrass fermentation exhibits a wide range of phytochemicals and bioactive components that effectively eliminate free radicals, despite the antioxidant content fluctuation throughout the fermentation period of t = 24 to t = 96 h.

Integrated volatile metabolome and transcriptome analyses provide insights into the warm aroma formation elicited by methyl jasmonate in carrot root

Carrot is a highly significant vegetable cultivated worldwide and possesses a unique aroma with abundant edible and medicinal values. However, it remains largely unknown whether jasmonic acid could regulate aroma formation in carrot. Here, an integrated analysis of the volatile metabolome and transcriptome of carrot roots exposed to different concentrations of methyl jasmonate (MeJA) was performed. The results revealed 1,227 volatile organic compounds and 972 differential accumulated metabolites, with terpenes representing the largest portion. MeJA treatment evidently increased the relative odor activity values as well as the accumulation of most volatile compounds. In addition, 4,787 differentially expressed genes were identified and subjected to function enrichment analysis, indicating a role of terpene biosynthesis and metabolism in response to MeJA application. A network consisting of 4,680 transcription factor-structural pairs that showed highly significant positive correlations was constructed, which may be utilized as genetic targets for examining terpene accumulation and aroma formation elicited by methyl jasmonate. The results from the present work substantially improved our understanding of MeJA-mediated aroma formation in carrot.

Characterization of Volatile Organic Compounds and Essential Oil Profile of Pittosporum tobira (Thunb.) W.T. Aiton Cultivated in Tunisia

The chemical compositions of the essential oils (EOs) of roots, young and old leaves and stems, and flowers of Pittosporum tobira (Thunb.) W.T. Aiton cultivated in Tunisia and of the volatile organic compounds (VOCs) emitted by the powder of each organ were identified. The EOs are extracted from fresh material by hydrodistillation, whereas the VOCs are obtained by head space solid-phase microextraction (HS-SPME) from the powdered dry tissues. Fifty-eight VOCs are identified, while, 105 components are detected for the EOs. The main EOs compounds are α-neoclovene, β-caryophyllene and limonene in roots (22.56, 12.52, and 8.59 %, respectively), viridiflorol in young stems, flowers and young leaves (34.90, 31.60, and 24.60 %, respectively), α-cadinol in young stems and leaves, and flowers (13.80, 10.40, and 9.10 %, respectively), (E)-nerolidol in flowers (13.30 %), and germacrene D in old stems (9.06 %). The major detected VOCs are n-undecane, mainly in young and old leaves (71.40 and 40.90 %, respectively), n-nonane in young leaves and flowers (31.80 and 27.10 %, respectively), α-cubebene in old stems and flowers (22.60 and 15.50 %, respectively), and α-gurjunene and β-gurjunene in roots (14.20 and 12.20 %, respectively). Principal Component Analysis (PCA) carried out on the 26 main volatile compounds (relative content exceeding 6 %) identified both by HS and in the EOs allowed their classification into two groups; compounds specific to roots and those specific to aerial parts. The later are subdivided in to two subgroups; old leaves and stems compounds subgroup, and young leaves and stems, and flowers one. We can notice that the two methods used to extract P. tobira volatile compounds and identify them are complementary. This study defines and differentiates, for the first time, the specific aroma profile of P. tobira from Tunisia. In addition to its ornamental value, all the organs of this species, could be valued as a source of volatile compounds useful in perfume, cosmetics and as food flavoring products.

Phytochemical Composition and Biological Activity

Phytochemicals are bioactive plant compounds that provide humans with health benefits, representing a valuable source of novel bioactive molecules [...].

Characterization of Volatile Organic Compounds in Five Celery (Apium graveolens L.) Cultivars with Different Petiole Colors by HS-SPME-GC-MS

Celery (Apium graveolens L.) is an important vegetable crop cultivated worldwide for its medicinal properties and distinctive flavor. Volatile organic compound (VOC) analysis is a valuable tool for the identification and classification of species. Currently, less research has been conducted on aroma compounds in different celery varieties and colors. In this study, five different colored celery were quantitatively analyzed for VOCs using HS-SPME, GC-MS determination, and stoichiometry methods. The result revealed that γ-terpinene, d-limonene, 2-hexenal,-(E)-, and β-myrcene contributed primarily to the celery aroma. The composition of compounds in celery exhibited a correlation not only with the color of the variety, with green celery displaying a higher concentration compared with other varieties, but also with the specific organ, whereby the content and distribution of volatile compounds were primarily influenced by the leaf rather than the petiole. Seven key genes influencing terpenoid synthesis were screened to detect expression levels. Most of the genes exhibited higher expression in leaves than petioles. In addition, some genes, particularly AgDXS and AgIDI, have higher expression levels in celery than other genes, thereby influencing the regulation of terpenoid synthesis through the MEP and MVA pathways, such as hydrocarbon monoterpenes. This study identified the characteristics of flavor compounds and key aroma components in different colored celery varieties and explored key genes involved in the regulation of terpenoid synthesis, laying a theoretical foundation for understanding flavor chemistry and improving its quality.

Light Regulation of LoCOP1 and Its Role in Floral Scent Biosynthesis in Lilium 'Siberia'

Light is an important environmental signal that governs plant growth, development, and metabolism. Constitutive photomorphogenic 1 (COP1) is a light signaling component that plays a vital role in plant light responses. We isolated the COP1 gene (LoCOP1) from the petals of Lilium 'Siberia' and investigated its function. The LoCOP1 protein was found to be the most similar to Apostasia shenzhenica COP1. LoCOP1 was found to be an important factor located in the nucleus and played a negative regulatory role in floral scent production and emission using the virus-induced gene silencing (VIGS) approach. The yeast two-hybrid, β-galactosidase, and bimolecular fluorescence complementation (BiFC) assays revealed that LoCOP1 interacts with LoMYB1 and LoMYB3. Furthermore, light modified both the subcellular distribution of LoCOP1 and its interactions with LoMYB1 and MYB3 in onion cells. The findings highlighted an important regulatory mechanism in the light signaling system that governs scent emission in Lilium 'Siberia' by the ubiquitination and degradation of transcription factors via the proteasome pathway.

Exploring Volatile Organic Compounds in Rhizomes and Leaves of Kaempferia parviflora Wall. Ex Baker Using HS-SPME and GC-TOF/MS Combined with Multivariate Analysis

Volatile organic compounds (VOCs) play an important role in the biological activities of the medicinal Zingiberaceae species. In commercial preparations of VOCs from Kaempferia parviflora rhizomes, its leaves are wasted as by-products. The foliage could be an alternative source to rhizome, but its VOCs composition has not been explored previously. In this study, the VOCs in the leaves and rhizomes of K. parviflora plants grown in a growth room and in the field were analyzed using the headspace solid-phase microextraction (HS-SPME) method coupled with gas chromatography and time-of-flight mass spectrometry (GC-TOF-MS). The results showed a total of 75 and 78 VOCs identified from the leaves and rhizomes, respectively, of plants grown in the growth room. In the field samples, 96 VOCs were detected from the leaves and 98 from the rhizomes. These numbers are higher compared to the previous reports, which can be attributed to the analytical techniques used. It was also observed that monoterpenes were dominant in leaves, whereas sesquiterpenes were more abundant in rhizomes. Principal component analysis (PCA) revealed significantly higher abundance and diversity of VOCs in plants grown in the field than in the growth room. A high level of similarity of identified VOCs between the two tissues was also observed, as they shared 68 and 94 VOCs in the growth room and field samples, respectively. The difference lies in the relative abundance of VOCs, as most of them are abundant in rhizomes. Overall, the current study showed that the leaves of K. parviflora, grown in any growth conditions, can be further utilized as an alternative source of VOCs for rhizomes.