Genus Rheum (Polygonaceae): A Global Perspective

161 Pages·2021·27.983 MB·English

by  Shahzad A. Pandith, Mohd. Ishfaq Khan, Salika Ramazan

Genus Rheum
(Polygonaceae)

Genus Rheum
(Polygonaceae)
A Global Perspective
Shahzad A. Pandith
Mohd Ishfaq Khan
First edition published 2022
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ISBN: 9780367355760 (hbk)
ISBN: 9780429340390 (ebk)
ISBN: 9781032058429 (pbk)
DOI: 10.1201/9780429340390
Typeset in Times
by Deanta Global Publishing Services, Chennai, India
Contents
Preface.................................................................................................................vii
Authors .................................................................................................................ix
Chapter 1 Introduction .....................................................................................1
1.1 Introduction ..........................................................................1
References .......................................................................................4
Chapter 2 Botany and Ecology ........................................................................7
2.1 Occurrence and Distribution ................................................7
2.2 Taxonomy and Classification ................................................7
2.3 Morphology ........................................................................14
2.4 Synonyms and Vernacular Names ......................................25
2.5 Pollen Studies .....................................................................25
2.6 Ecology ...............................................................................33
References .....................................................................................34
Chapter 3 Traditional Uses .............................................................................39
3.1 Rhubarb as a Food Plant .....................................................42
References .....................................................................................44
Chapter 4 Phytochemistry ..............................................................................47
4.1 Phenolics .............................................................................48
4.2 Anthraquinones ..................................................................61
4.3 Stilbenoids ..........................................................................62
4.4 Other Constituents ..............................................................65
4.4.1 Anthraglycosides ...................................................70
4.4.2 Dianthrones ...........................................................71
References .....................................................................................71
Chapter 5 Pharmacology ................................................................................75
5.1 Antimicrobial Activity .......................................................75
5.2 Anticancer Activity ............................................................77
5.3 Antidiabetic Activity ..........................................................80
5.4 Anti-Inflammatory Activity ...............................................83
5.5 Antioxidative Activity ........................................................84
5.6 Immunoenhancing Activity ................................................87
5.7 Nephroprotective Activity ..................................................87
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vi Contents
5.8 Hepatoprotective Activity ...................................................90
5.9 Miscellaneous Activities ....................................................92
References .....................................................................................94
Chapter 6 Molecular Aspects .......................................................................107
6.1 Cytogenetics .....................................................................107
6.2 Genetics .............................................................................110
6.2.1 Rhubarb in the Wild .............................................111
6.2.2 Rhubarb Cultivars ................................................114
6.3 Biotechnological Interventions ..........................................119
References ...................................................................................126
Chapter 7 Conservation ................................................................................135
7.1 Threat Status .....................................................................135
7.2 In vitro Propagation Studies as a
Conservation Measure ......................................................136
References ...................................................................................138
Chapter 8 Conclusions and Future Prospects................................................141
References ...................................................................................146
Preface
Plants, sessile but promising organisms, have been well-known for benefiting
human existence in the form of a variety of natural products for ages. Among
this vast reservoir of natural economic wealth, rhubarb (Polygonaceae) is one
of the important medicinal herbs with an intricate historical background and an
immense value for the associated societies for centuries. Rhubarb, a significant
object of botanical, commercial, and horticultural interest, is presently repre-
sented by about 60 extant species occurring across Asian and European countries
with a major distribution found in the mountainous regions of the Qinghai-
Tibetan Plateau in China. This perennial species is documented for use in various
traditional medical systems from varied cultures across different regions as one
of the most sought-after crude drugs due to its mildness, efficacy, and lack of
unwanted side effects. Indeed, in therapeutic history, there has probably been no
medicine which has provided better relief to more people than the rhizome/root
powder made from medicinal rhubarb (Rheum officinale). Moreover, there has
been remarkable interest from researchers around the world in some of the highly
medicinal herbs from this genus which, although not limited to, include R. aus-
trale, R. tanguticum, R. palmatum, and R. officinale, among others. Pertinently,
the remedying properties of Rheum are attributed to a group of diverse biologi-
cally active secondary chemical constituents, predominantly anthraquinones, and
stilbenoids to a lesser extent, as well as the dietary flavonoids known for their puta-
tive health benefits. But unfortunately, human greed has prevailed and rendered
some of the important species from this Polygonaceous herb threatened in the
natural stands, causing the need for their conservation. Further, with the advance-
ment of the state-of-the-art scientific techniques, current and related research is
mainly focused on various promising metabolic pathways from medicinal plants
like Rheum to decipher the biosynthesis of their key bioactive chemical constitu-
ents, which may help in modulating the specific pathways in alternate (microbial)
hosts while preserving the natural wild stock.
This book is literally the biography of the rhubarb plant and presents a global
perspective of this important medicinal herb while covering almost every aspect,
ranging from its history to the application of contemporary biotechnological
interventions. It provides updated information on nearly all aspects of the plant
covering varied forms of related literature since the 18th century, and include:
• The historical background detailing its earlier trade and commerce;
• Global distribution giving an idea of the source of its origin and
dissemination;
• Botany for classical taxonomic aspects;
• Ecology to understand the ecological and evolutionary implications;
• Ethnobotany, phytochemistry and pharmacology vis-à-vis therapeutic
potential;
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• Genetic diversity with regard to the polymorphism and ploidy status
gained across varied geographies;
• Biotechnological invasions to assess the success level we have achieved
so far in accepting and utilizing rhubarb as a suitable drug reservoir; and
• In vitro propagation studies as a conservation and exploitation (at indus-
trial scale) measure.
We are hopeful that it will prove to be of great help to the researchers working
on rhubarb.
Shahzad A. Pandith
Mohd Ishfaq Khan
Authors
Shahzad A. Pandith received his MSc in botany from the University of Kashmir,
Srinagar, India, in 2009, and PhD in plant molecular biology from CSIR Indian
Institute of Integrative Medicine, Jammu, India, in 2017. He has since served
in the Department of Botany, University of Kashmir as DST-INSPIRE Faculty
(position equivalent to IITian assistant professor). In this capacity, he supervises
a DST-sponsored project on one of the important medicinal herbs from the north-
western Himalayas, Rheum. In general, Pandith seeks to use various “omics”
approaches to elucidate and understand the basic biology of plants, important
pathways operating in them and their modulation, rate-limiting pathway genes,
and the regulatory factors controlling their constitutive/inducible expression vis-
à-vis ecological/environmental factors and/or stress conditions. He has published
about 15 research papers in highly reputed peer-reviewed international journals
with an average impact of around three per paper. In addition, he is an active
reviewer of many reputed journals from well-known publishing houses like
Springer, Elsevier, and Brill, etc. Shahzad has many national-level exams and
awards to his credit, which include the Joint CSIR-UGC JRF and ICAR-ASRB
NET exams, and the highly prestigious DST-INSA INSPIRE Faculty award.
Mohd Ishfaq Khan holds a BSc degree from the University of Kashmir,
Srinagar, India, and received his MSc degree in botany from the same institu-
tion in 2015. Since 2017, he is actively engaged in a DST-sponsored project at
the University of Kashmir. His active areas of research include DNA barcoding,
genetics, taxonomy, and eco-physiology which he uses to understand and resolve
the genetic/taxonomic complexity in high-value medicinal herbs from the north-
western Himalayas. He has some good research articles to his credit. In addition,
he has qualified in many competitive exams at state and national level including
the Graduate Aptitude Test in Engineering (GATE)-2019 in the subject of life
sciences. Khan also holds a bachelor’s degree in education and has been a good
teacher-cum-motivator for students at higher secondary level.
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