glycosides introduction

Glycosides

Glycosides are a group of compounds consisting of sugar portion (or

moiety) attached by special bond to one or more non sugar portions.

Glycosides are broken down upon hydrolysis with enzymes or

acids to;1. Sugar moiety = glycone

2. Non-sugar moiety = aglycone/ active portion. This may be a

phenol, alcohol, or sulphur coumpounds.

• The bond between the two moieties may involve a phenolic hydroxyl group in which case a O-glycoside, similarly carbone (C-glycosides), nitrogen (N-glycosides) or sulphur (S-glycosides) may be involved.

• Widepread througout the plants, some may be toxic, cooking usually renders them non-toxic. Mostly soluble in water, though aglycones are less soluble.

Classification of glycosides

• Based on the nature of aglycone, same botanical families consistently contain the same aglycone

• Brassicaceae - glucosinolate

• Rosaceae - cyanogenic

• Scrophulariaceae - cardiac, phenylpropanoid

• Asteraceae - pheenylpropanoid, flavonoid

• Malvaceae - anthocyanin

• Cyanogenic glycosides

• Cardiac glycosides

• phenylpropanoid glycosides

• anthroquinones (anthracene glycosides)

• flavonoids (occur free or as glycosides)

• glucosinolates (mustards)

• iridoid glycosides (bitter)