The Occurrence of Methyl Salicylate in a Fern, Asplenium lamprophyllum.
[Read before the Auckland Institute, October 16, 1946; received by the Editor, October 29, 1946; issued separately, September, 1947.]
Following a field observation by Mr. O. J. Baker, M.Sc., that the odour of oil of wintergreen could be detected in the freshly broken stalks of the fern, Asplenium lamprophyllum, the presence of methyl salicylate (as its hydrolytic products) has now been confirmed by chemical means, the second record of this constituent in the whole order of ferns (cf. Freise, 1934). The odour is perceptible immediately the stalks are broken and is therefore due to the presence of free methyl salicylate and not to its glucoside, monotropitoside, which liberates the same aglycone after enzymatic hydrolysis (Klein, 1932). Attempts to isolate the glycoside following the procedure of Bridel (1923–24) were unsuccessful.
A. bulbiferum, which is almost indistinguishable from A. lampro-phyllum on morphological grounds, on the other hand, does not possess the same odour nor could methyl salicylate be detected chemically. Field tests by smell and taste on A. lucidum, A. flaccidum, and A. falcatum were also negative.
Nine pounds of the stalks of A. lamprophyllum, collected in the Mount Wellington area near Auckland, were steam distilled for seven hours. The distillate (700 c.c.) was neutralised with N/30 sodium hydroxide (53 c.c.), refluxed for two hours and then fractionated through a 27-plate column. The first fraction (250 mg.) had b.p. 72–83° /760 mm. with the temperature rising to 90° during the distillation of the next 200 mg. Excess of 3: 5-dinitrobenzoyl chloride in pyridine was added to the first fraction and allowed to stand for two days. On addition of water, methyl-3: 5-dinitrobenzoate was precipitated which, after crystallisation from 80 per cent. alcohol, had m.p. 107°, undepressed by an authentic sample.
The first fraction also gave iodoform, m.p. 118°, with sodium hypoiodate and a yellow precipitate with Brady's reagent not further examined.
The alkaline distilland was evaporated to dryness and acidified. It then yielded to ether 26 mg. of salicylic acid which, after purification by vacuum sublimation had m.p. 158°, undepressed by an authentic specimen.
We are indebted to the Chemical Society for a grant and one of us (W. I. T.) for a Duffus Lubecki Scholarship.
Bridel, M., 1923. Compt. rend., 177, 642.
—— 1924. Ibid., 178, 1310.
Freise, F. W., 1934. Sci. pharmaceutica, 5, 129.
Kelin, G., 1932. Handbuch der Pflanzenanalyse, Springer, Vienna, vol. 3, p. 821.