HS-SPME-GC-MS and Electronic Nose Reveal Differences in the Volatile Profiles of Hedychium Flowers

Floral fragrance is one of the most important characteristics of ornamental plants and plays a pivotal role in plant lifespan such as pollinator attraction, pest repelling, and protection against abiotic and biotic stresses. However, the precise determination of floral fragrance is limited. In the present study, the floral volatile compounds of six Hedychium accessions exhibiting from faint to highly fragrant were comparatively analyzed via gas chromatography-mass spectrometry (GC-MS) and Electronic nose (E-nose). A total of 42 volatile compounds were identified through GC-MS analysis, including monoterpenoids (18 compounds), sesquiterpenoids (12), benzenoids/phenylpropanoids (8), fatty acid derivatives (2), and others (2). In Hedychium coronarium 'ZS', H. forrestii 'Gaoling', H. 'Jin', H. 'Caixia', and H. 'Zhaoxia', monoterpenoids were abundant, while sesquiterpenoids were found in large quantities in H. coccineum 'KMH'. Hierarchical clustering analysis (HCA) divided the 42 volatile compounds into four different groups (I, II, III, IV), and Spearman correlation analysis showed these compounds to have different degrees of correlation. The E-nose was able to group the different accessions in the principal component analysis (PCA) corresponding to scent intensity. Furthermore, the pattern-recognition findings confirmed that the E-nose data validated the GC-MS results. The partial least squares (PLS) analysis between floral volatile compounds and sensors suggested that specific sensors were highly sensitive to terpenoids. In short, the E-nose is proficient in discriminating Hedychium accessions of different volatile profiles in both quantitative and qualitative aspects, offering an accurate and rapid reference technique for future applications.

Species complex delimitations in the genus Hedychium: A machine learning approach for cluster discovery

PREMISE

Statistical methods used by most morphologists to validate species boundaries (such as principal component analysis [PCA] and non-metric multidimensional scaling [nMDS]) are limiting because these methods are mostly used as visualization methods, and because the groups are identified by taxonomists (i.e., supervised), adding human bias. Here, we use a spectral clustering algorithm for the unsupervised discovery of species boundaries followed by the analysis of the cluster-defining characters.

METHODS

We used spectral clustering, nMDS, and PCA on 16 morphological characters within the genus Hedychium to group 93 individuals from 10 taxa. A radial basis function kernel was used for the spectral clustering with user-specified tuning values (gamma). The goodness of the discovered clusters using each gamma value was quantified using eigengap, a normalized mutual information score, and the Rand index. Finally, mutual information-based character selection and a t-test were used to identify cluster-defining characters.

RESULTS

Spectral clustering revealed five, nine, and 12 clusters of taxa in the species complexes examined here. Character selection identified at least four characters that defined these clusters.

DISCUSSION

Together with our proposed character analysis methods, spectral clustering enabled the unsupervised discovery of species boundaries along with an explanation of their biological significance. Our results suggest that spectral clustering combined with a character selection analysis can enhance morphometric analyses and is superior to current clustering methods for species delimitation.

Uncharted Source of Medicinal Products: The Case of the Hedychium Genus

A current research topic of great interest is the study of the therapeutic properties of plants and of their bioactive secondary metabolites. Plants have been used to treat all types of health problems from allergies to cancer, in addition to their use in the perfumery industry and as food. Hedychium species are among those plants used in folk medicine in several countries and several works have been reported to verify if and how effectively these plants exert the effects reported in folk medicine, studying their essential oils, extracts and pure secondary metabolites. Hedychium coronarium and Hedychium spicatum are the most studied species. Interesting compounds have been identified like coronarin D, which possesses antibacterial, antifungal and antitumor activities, as well as isocoronarin D, linalool and villosin that exhibit better cytotoxicity towards tumor cell lines than the reference compounds used, with villosin not affecting the non-tumor cell line. Linalool and α-pinene are the most active compounds found in Hedychium essential oils, while β-pinene is identified as the most widespread compound, being reported in 12 different Hedychium species. Since only some Hedychium species have been investigated, this review hopes to shed some light on the uncharted territory that is the Hedychium genus.

Complete chloroplast genome sequence of Hedychium coronarium

The first complete chloroplast genome of Hedychium coronarium (Zingiberaceae) was reported in this study. The H. coronarium chloroplast genome was 163,949 bp in length and comprised a pair of inverted repeat (IR) regions of 29,780 bp each, a large single-copy (LSC) region of 88,581 bp and a small single-copy (SSC) region of 15,808 bp. It encoded 141 genes, including 87 protein-coding genes (79 PCG species), 46 tRNA genes (28 tRNA species), and eight rRNA genes (four rRNA species). The nucleotide composition was asymmetric (31.68% A, 18.35% C, 17.74% G, 32.23% T) with an overall AT content of 63.92%. Phylogenetic analysis showed that H. coronarium was classified into a monophyletic group within the genus Hedychium in family Zingiberaceae.

Hedychium putaoense (Zingiberaceae), a new species from Putao, Kachin State, Northern Myanmar

Hedychium putaoense Y.H. Tan & H.B. Ding, a new species of Zingiberaceae from Putao, Kachin state, Northern Myanmar, is described and illustrated. It is similar to H. densiflorum Wall. and H. longipedunculatum A.R.K. Sastry & D.M. Verma, but differs by its very small bract (4-6 × 2.5-3 mm vs. 18-19 × 5-5.5 mm and ca. 11 × 7 mm, respectively), semicircle and dark red bracteole, orange flower and broadly falcate to lanceolate lateral staminodes.

Genetic diversity and relationship of Hedychium from Northeast India as dissected using PCA analysis and hierarchical clustering

Molecular genetic fingerprints of eleven Hedychium species from Northeast India were developed using PCR based markers. Fifteen inter-simple sequence repeats (ISSRs) and five amplified fragment length polymorphism (AFLP) primers produced 547 polymorphic fragments. Positive correlation (r = 0.46) was observed between the mean genetic similarity and genetic diversity parameters at the inter-species level. AFLP and ISSR markers were able to group the species according to its altitude and intensity of flower aroma. Cophenetic correlation coefficients between the dendrogram and the original similarity matrix were significant for ISSR (r = 0.89) compared to AFLP (r = 0.83) markers. This genetic characterization of Hedychium from Northeast India contributes to the knowledge of genetic structure of the species and can be used to define strategies for their conservation and management.

Composition of essential oils of four Hedychium species from Vietnam

Background

Vietnam is a country blessed with many medicinal plants widely used as food and for medicinal purposes, and they contain a host of active substances that contribute to health. However, the analysis of chemical constituents of these plant species has not been subject of literature discussion.

Results

In this study, the chemical compositions of essential oils of four Hedychium species, obtained by hydrodistillation, were determined by means of gas chromatography-flame ionization detector (GC-FID) and gas chromatography–mass spectrometry (GC-MS) techniques. Individually, α-pinene (52.5%) and β-pinene (31.8%) were present in the leaf oil of Hedychium stenopetalum Lodd., while linalool (45.2%), (E)-nerolidol (8.7%) and α-pinene (5.0%) were identified in the root. The leaf of Hedychium coronarium J. König was characterized by β-pinene (20.0%), linalool (15.8%), 1,8-cineole (10.7%), α-pinene (10.1%) and α-terpineol (8.6%); while β-pinene (23.6%), α-humulene (17.1%) and β-caryophyllene (13.0%) were identified in the root. Hedychium flavum Roxb., gave oil whose major compounds were β-pinene (22.5%), α-humulene (15.7%) and β-caryophyllene (10.4%) in the leaf; α-humulene (18.9%), β-caryophyllene (11.8%) and β-pinene (11.2%) in the stem, as well as β-pinene (21.8%), linalool (17.5%) and 1,8-cineole (13.5%) in the root. The main constituents of Hedychium ellipticum Buch.-Ham. ex Smith were (E)-nerolidol (15.9%), β-pinene (11.8%) and bornyl acetate (9.2%) in the leaf with 1,8-cineole (40.8%), α-pinene (18.3%) and β-pinene (11.0%) occurring in the root.

Conclusions

Ubiquitous monoterpenes and sesquiterpenes were identified as characteristic markers for Hedychium species. This work is of great importance for the evaluation of Hedychium essential oils grown in Vietnam.

Electronic supplementary material

The online version of this article (doi:10.1186/s13065-014-0054-3) contains supplementary material, which is available to authorized users.

tenuiflorum (Zingiberaceae)

The evolutionary advantages of polyploidy may result from a number of changes in floral traits and breeding system, which may enable polyploids to exploit new habitats and become widespread. In this study, we comparatively investigated the floral biology of the tetraploid species Hedychium villosum and its diploid progenitor H. tenuiflorum, to assess reproductive divergence between the two species. The results showed that flowers of the tetraploid species last longer and produce more nectar than did diploid species. The flowering times of the two species did not overlap at all. Observations of floral visitors in natural populations demonstrated that butterflies and hawkmoths were effective pollinators of both species, but there was a significant difference in butterfly and hawkmoth assemblages between the two species. The hand-pollination experiments and pollen tube growth experiments suggested that diploid H. tenuiflorum was self-incompatible, while tetraploid H. villosum was completely self-compatible. H. villosum has a much wider distribution range and occupies more diverse habitats than H. tenuiflorum. Polyploidisation may enable tetraploid H. villosum to exploit new habitats previously unavailable to diploid H. tenuiflorum.