PLANT SECONDARY METABOLITES

Plant Secondary Metabolites as Natural Products

CHAPTER 1: INTRODUCTION3

Background of the Research3

Significance of the Research4

Aim & Objectives5

CHAPTER 2: LITERATURE REVIEW6

Prospecting genetic variability6

Establishment of in vitro cell lines6

Cell suspension cultures8

Induction and establishment of hairy root cultures9

Shoot cultures10

Influence of different medium constituents on growth and production of betalains10

Stability studies of betalains obtained from hairy root cultures of Beta vulgaris L.12

Influence of iron and copper on antioxidant enzymes13

Protocol for micropropagation of Beta vulgaris L.13

CHAPTER 3: METHODOLOGY15

Overview of Qualitative and Quantitative Research Approaches15

Overview of the Mixed Method Research Approach16

Benefits and Disadvantages of Mixed Method16

Confidentiality17

Validity18

Reliability18

CHAPTER 1: INTRODUCTION

Background of the Research

Plants are a vast resource of a number of chemical substances, which may be primary or secondary metabolites. Primary metabolites are those, which are directly synthesized and encoded by their respective genes or by basic photosynthetic process. Secondary metabolites are produced by plants, which play a major role in the defense mechanisms and adaptation of plants to their environment. These molecules largely contribute to plant fitness by interacting with the ecosystem (Meyer, 1998). The plant secondary metabolites have been classified according to their biosynthetic pathways. Four large families are generally considered i.e. phenolics, terpenes, sterols and alkaloids. Plant secondary metabolites have been used from centuries in traditional medicine due to their large biological activities. They are also useful as food additives, flavours, colourants and pharmaceuticals. It has been established that despite rapid progress in applied chemistry 25% of the molecules used in pharmaceutical industry are still of plant origin (Curtis, 1999).

Conventionally plant secondary metabolites are obtained from field grown plants. However recently plant cell cultures have been exploited for the production of various secondary metabolites of food and pharmaceutical importance. Roots are the most important part of the plant system and are a source of many valuable products such as pharmaceuticals, insecticides, colours, flavours, enzymes and others. They are the major sites of metabolite synthesis and storage, which exhibit indefinite growth because of the meristamatic activity of root tip meristem. Many compounds that are scarcely synthesized such as coumarins, caffeic acid esters and cathecins in undifferentiated cells are produced at higher levels in root cultures (Bourgaud, 1999).

Significance of the Research

Among the in vitro culture systems, the cultured cell suspensions are not gained momentum because of their instability and non-uniformity of the product formation. Hence the differentiated organ cultures such as hairy root cultures are widely studied. Hairy root cultures are used as alternative production systems for secondary metabolites due to their tremendous potential to higher growth rate and uniform product formation. Being organized, they are amenable for scaling-up in bioreactors which is an added advantage. The metabolite pattern found in hairy roots is similar, if not always identical to that of plant roots. A major characteristic of hairy roots is the concomitant production of secondary metabolites with growth. Hence it is possible to get a continuous source of secondary metabolites from actively growing hairy roots (Curtis, 1999).

Colour in one form or the other has been added in foods for ...