ソルガム属飼料作物およびクローバー類の精油成分とその質量分析 <総説>

ソルガム属飼料作物およびクローバー類の各生草を水蒸気蒸留して、それぞれの精油を得た。精油はその全体をガスクロマトグラフ質量分析計(GC/MS)で、さらに酸性、フェノール性、塩基性、非極性および極性部に分画して、各フラクションをGC/MSで分析した。そのマススペクトルより、ソルガム属飼料作物から16種の炭化水素類、5種のアルデヒド類、7種のケトン類、6種のアルコール類、11種のエステル類、6種のフェノール類および14種の酸類の計65化合物を固定した。(KAMI, 1975; 1977)。一方、クローバー類から15種の炭化水素類、8種のアルデヒド類、2種のケトン類、7種のアルコール類、37種のエステル類、1種のフェノール類および20種の酸類の計90化合物を固定した。(KAMI, 1978)。両飼料作物の精油成分を比較すると、ソルガム属飼料作物はケトン類とフェノール類を数多く含有し、クローバー類はエステル類を数多く含有していた。本論分は、これら同定した化合物の膨大な分析データを整理したものである。

The second crops of Hybridsorgo and Sudangrass, forage sorghums, and the first crops of red and Ladino white clovers were, respectively, distilled with steam to collect the essen-tial oils. The essential oils were analyzed by combined gas chromatography-mass spec-trometry, directly or after the fractionation into acidic, phenolic, basic, nonpolar, and polar fractions. From the essential oils of forage sorghums, 65 compounds consisting of 16 hydrocarbons, 5 aldehydes, 7 ketones, 6 alcohoIs, 11 esters, 6 phenols, and 14 acid were identified through comparison of mass spectra with authentic spectra (KAMI, 1975; 1977). On the other hand, from the essential oils of clovers, 90 compounds consisting of 15 hydrocarbons, 8 aldehydes, 2 ketones. 7 alcohols, 37 esters, phenol. and 20 acids were iden-tified (KAMI, 1978) In comparison of the components of forage sorghums and clovers, many ketones and phenols were contained in sorghums, while many esters were contained in clovers.

The mass spectra of identified compounds by functional groups are explained as fellows.

1. Aliphatic saturated hydrocarbons have the base (largest) peak at m/z (mass-to-charge ratio) 57, and then follow at m/z 43, 71, and 85. The major peaks in the high mass region occur at intervals of 14 mass units. The molecule ion peak of aromatic hydrocarbons is very large, in contrast to aliphatic hydrocarbons. This difference is attributed to the stability of the benzene ring, the effect being general in most aromatic compounds. Aromatic hydrocarbons appear the base peak or the large peak at m/z 91.

2. Aliphatic aldehydes from C1 to C3 have the base peak at m/z 29, normal aldehydes from C4 to C6 at m/z 44, and normal aldehydes more than C7 at m/z 43 or 57, respectively. The base peak of aromatic aldehydes is frequently the [M-29]+ (the loss of mass 29 from molecular ion).

3. Aliphatic ketones have the base peak at m/z 43. In addition, methyl ketones produce a characteristic rearrangement peak at m/z 58 and ethyl ketones at m/z 72, respectively.

4. Aliphatic alcohols less than n-C4 have the base peak at m/z 31 and the base peak of normal alcohols more than C5 is an olefin-type peak (m/z 41, 42, 55, 56). The base peak of aromatic alcohols is the [M-29]+ or [M-31]+.

5. The methyl esters of long-chain carboxylic acids (pentanoates and higher) have the base peak at m/z 74, the ethyl esters of long-chain carboxylic acids (hexanoates and higher) at m/z 88 or 43, and acetates at m/z 43, respectively. The base peak of the methyl esters of aromatic acids is the [M-31]+ or [M-59]+, the base peak of the ethyl esters of aromatic acids is the [M-45]+ or [M-73]+.

6. In phenols, cresols have the base peak or the large peak at [M-1]+, and ethyl and dimethyl phenols at [M-15]+, respectively.

7. Long-chain normal carboxylic acids (butyric acid and higher) have the base peak at m/z 60. In aromatic acids, only benozoic acid was directly identified by GC/MS but the other acids were identified from the methyl esters of the acids.