=Coniferin=, C_{16}H_{22}O_{8} (glucose and coniferyl alcohol), is found in the bark of fir trees. The coniferyl alcohol obtained from coniferin by hydrolysis can be easily oxidized to _vanillin_, and is, therefore, the source for the artificial flavoring extract used as a substitute for the true extract of the vanilla bean. =Populin=, C_{20}H_{22}O_{8} (glucose+saligenin+benzoic acid), found in the bark of poplar trees, is used in medicine as an antipyretic. It can be hydrolyzed, by a special enzyme, into salicin and benzoic acid. The structure of the two typical closed-ring alcohols which are present in these glucosides is indicated by the following formulas; Coniferyl alcohol Saligenin CH=CH·CH_{2}OH /\ /\ / \ / \ | |CH_{2}OH | | | |OX | |OCH_{3} \ / \ / \/ \/ OX THE ALDEHYDE GLUCOSIDES =Salinigrin=, C_{13}H_{16}O_{7} (glucose and _m_-oxy benzaldehyde), is found in the bark of one species of willow (_Salix discolor_). Its isomer, known as _helicin_ (glucose and _o_-oxy benzaldehyde, or salicylic aldehyde), does not occur naturally in any plant, but is easily produced artificially by the gentle oxidation of salicin. Their relationships are shown on the following formulas; Salicin Helicin Salinigrin /\ /\ /\ / \ / \ / \ | |CH_{2}OH | |CHO | |CHO | |OX | |OX | | \ / \ / \ / \/ \/ \/ OX =Amygdalin=, also contains a benzaldehyde group, but there is linked with it a hydrocyanic acid group; hence, this glucoside is usually classed with the cyanophoric glucosides (see page 86). THE ACID GLUCOSIDES The most common example of this group is =gaultherin=, C_{14}H_{18}O_{8}, which is found in the bark of the black birch and is a combination of glucose with methyl salicylate. Both the glucoside itself and the methyl salicylate ("oil of wintergreen") which is derived from it are used as remedies for rheumatism. =Jalapin=, C_{44}H_{56}O_{16} (glucose and jalapinic acid), and =convolvulin=, C_{54}H_{96}O_{27} (glucose+rhodeose+convolvulinic acid), are glucosides of very complex organic acids, found in jalap resin, which are used in medicine as cathartics or purgatives. THE OXY-CUMARIN GLUCOSIDES