Medicinal Plants

Chemistry, Biology and Omics

Da-Cheng Hao, Xiao Jie Gu, Pei Gen Xiao

• Publisher: Woodhead Publishing
• Year: 2015
• ISBN:
  9780081001035
• Topic: Biological Sciences
• Subtopic: Botany
• Index: Biological Sciences

Medicinal Plants: Chemistry, Biology and Omics reviews the phytochemistry, chemotaxonomy, molecular biology, and phylogeny of selected medicinal plant tribes and genera, and their relevance to drug efficacy.

Medicinal plants provide a myriad of pharmaceutically active components, which have been commonly used in traditional Chinese medicine and worldwide for thousands of years. Increasing interest in plant-based medicinal resources has led to additional discoveries of many novel compounds, in various angiosperm and gymnosperm species, and investigations on their chemotaxonomy, molecular phylogeny and pharmacology.

Chapters in this book explore the interrelationship within traditional Chinese medicinal plant groups and between Chinese species and species outside of China. Chapters also discuss the incongruence between chemotaxonomy and molecular phylogeny, concluding with chapters on systems biology and "-omics" technologies (genomics, transcriptomics, proteomics, and metabolomics), and how they will play an increasingly important role in future pharmaceutical research.

• Reviews best practice and essential developments in medicinal plant chemistry and biology
• Discusses the principles and applications of various techniques used to discover medicinal compounds
• Explores the analysis and classification of novel plant-based medicinal compounds
• Includes case studies on pharmaphylogeny
• Compares and integrates traditional knowledge and current perception of worldwide medicinal plants

1

Chemotaxonomy

a phylogeny-based approach

Abstract

This chapter summarizes the chemotaxonomic study of medicinal plants and focuses on the chemical classification, as well as its relationship with morphology-based taxonomy and molecular biology classification. Both primary metabolites and secondary metabolites (SMs) are used as chemotaxonomic markers. Fatty acid, alkane, and alkyne are most commonly used primary metabolites. In comparison, more categories of SM are used in chemotaxonomy, such as essential oil and volatile terpene, diterpene, triterpene/saponin, alkaloid, flavonoid, lignin, and phenolics. The combined use of various classification methods could provide most robust taxonomy system. Developing metabolomics and cheminformatics tools, as well as constructing relevant databases, is highlighted in the new trend of chemotaxonomy. Due to the short supply of plant-based drugs in the current market, the medicinal plant classification studies should highlight combining pharmacological research to expand the herbal drug sources.

Keywords

Chemotaxonomy

Secondary metabolite

Phylogeny

Metabolomics

Medicinal plant

1.1 Introduction

Chemotaxonomy, also called chemosystematics, is used to classify and identify organisms (mainly plants), according to perceptible differences and similarities in their biochemical compositions. The compounds studied in all cases are either primary metabolites or secondary metabolites (SMs). Examples of chemotaxonomic markers used in recent years are summarized below. Chemotaxonomy contributes to the classification of plants when uncertainty exists using classical botanical methods. Chemosystematics can be regarded as a fusion science that complements available morphological and molecular data to improve plant systematics and to facilitate pharmaceutical resource discovery.

1.2 Chemotaxonomic marker

1.2.1 Primary metabolite

1.2.1.1 Fatty acid

Among the various biochemical markers, fatty acids (FAs) or lipid profiles represent a chemically relatively inert class of compounds that is easy to isolate from biological material. FA (Figure 1.1) profiles are chemotaxonomic markers that define groups of various taxonomic ranks in flowering plants, trees, and other embryophytes. The FA profiles of 2076 microalgal strains from the Culture Collection of Algae at Göttingen University (SAG) were determined in the stationary phase (Lang et al., 2011). Seventy-six different FAs and 10 other lipophilic substances were identified and quantified. The FA profiles were added into a database. FA distribution patterns were found to reflect phylogenetic relationships at the level of phyla and classes. At lower taxonomic levels, for example, between closely related species and among multiple isolates of the same species, FA contents may be rather variable. FA distribution patterns are suitable chemotaxonomic markers to define taxa of higher rank in algae. Due to their extensive variation at the species level, it is difficult to make predictions about the FA profile in a novel isolate.

Figure 1.1 Fatty acids.

The distribution of FAs in 13 species of macroalgae (Chlorophyta, Ochrophyta, and Rhodophyta) and one sea grass (Spartina sp.), collected on the Rio de Janeiro state coast, was determined (Fleury et al., 2011). Statistical analyses showed the effectiveness as taxonomic and phylogenetic markers of the distribution of the methyl FA esters in these macrophytes.

In Geranium (Geraniaceae) and highly related Erodium taxa from Serbia and Macedonia, the investigated essential oils consisted mainly of FAs and FA-derived compounds (45.4–81.3%), with hexadecanoic acid and (E)-phytol as the major components (Radulović and Dekić, 2013). Geranium and Erodium taxa are phylogenetically closely related, and there is no great intergeneric oil-composition variability.

The FA composition of 12 Brassica species (Brassicaceae) was analyzed by GC-FID and confirmed by gas chromatography–mass spectrometry (GC–MS) (Barthet, 2008). According to the C18:1 (n − 7)/(n − 9) ratios for chemotaxonomy, the surveyed species could be arranged into three groups. The first group includes Brassica napus, B. rapa, and B. tournefortii with Eruca sativa branching only related to B. napus. The second group includes B. tournefortii, Raphanus sativus, and Sinapis alba. The last group includes B. juncea, B. carinata, and B. nigra with no similarity/relationship between them and between the other species.

The FA composition of the seed oil of 23 Stachys (Labiatae) taxa was analyzed by GC–MS (Gören et al., 2012). The main compounds were linoleic (27.1–64.3%), oleic (20.25–48.1%), palmitic (4.3–9.1%), stearic (trace to 5.2%), and 6-octadecynoic (2.2–34.1%) acids. The latter compound could be a chemotaxonomic marker of the genus Stachys.

FAs and sterols were determined in 59 genotypes of 17 distinct Coffea species (Rubiaceae) (Dussert et al., 2008). Interestingly, while groupings based on seed FA composition showed remarkable ecological and geographic coherence (Figure 1.2), no phylogeographic explanation was found for the clusters retrieved from sterol data. When compared with previous phylogenetic studies, the groups deduced from seed FA composition were remarkably congruent with the clades inferred from nuclear and plastid DNA sequences (Table 1.1). Leaf FA composition is useful in chemotaxonomy of Rubiaceae (Mongrand et al., 2005). Principal component analysis (PCA) allowed a clear-cut separation of Coffeae, Psychotrieae, and Rubieae.

Figure 1.2 A simplified scheme showing the hierarchical clustering analysis of the seed fatty acid composition of 59 Coffea genotypes (according to Dussert et al., 2008). Correspondence between groups of species obtained through HCA of seed FA data and clades inferred from DNA sequences (Maurin et al., 2007) is shown.

Table 1.1

Distribution of phenylethanoid glycoside in Gesneriaceae species

Species	Acteoside	Paraboside B	Isonuomioside A	Paraboside II	Paraboside III
Beccarinda tonkinensis	*	_	_	_	_
Hemiboea subcapitata	*	_	_	_	_
Hemiboea flaccida	*	_	*	_	_
Chirita macrodonta	*	_	_	_	_
Chirita pumila	*	_	_...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Preface
• 1: Chemotaxonomy: a phylogeny-based approach
• 2: High-throughput sequencing in medicinal plant transcriptome studies
• 3: Taxus medicinal resources: a comprehensive study
• 4: Phytochemical and biological research of Fritillaria medicinal resources
• 5: Phytochemical and biological research of Chelidonieae pharmaceutical resources
• 6: Phytochemical and biological research of Papaver pharmaceutical resources
• 7: Chemical and biological studies of Aconitum pharmaceutical resources
• 8: Chemical and biological studies of Cimicifugeae pharmaceutical resources
• 9: Chemical and biological research of Clematis medicinal resources
• 10: Potentilla and Rubus medicinal plants: potential non-Camellia tea resources
• 11: Phytochemical and biological research of Cannabis pharmaceutical resources
• 12: Phytochemical and biological research of Polygoneae medicinal resources
• 13: Phytochemistry and biology of Ilex pharmaceutical resources
• 14: Phytochemical and biological research of Salvia medicinal resources
• 15: Phytochemical and biological research of Panax medicinal resources
• Index