| Piper longum L. is one of the ripen fruit of the Piperaceae plant. The herb acts on dispersing cold and relieving pain. It is widely used to treat vomit, diarrhea, migraine, toothache and so on. Meanwhile, modern research also shows that Piper longum L. has many pharmacological activities.The volatile oils from Piper longum L.were analyzed and studied in the paper. The volatile oils from Pericarpium Piper longum L. were respectively extracted by hydrodistillation and microwave assisted extraction in a two-stage separation system. The each optimum extraction process for volatile oil obtained by hydrodistillation or microwave assisted extraction methods was investigated by the simple factor experiment and orthogonal design. The chemical constituents of volatile oils were separated and identified by gas chromatography-mass spectrometry (GC-MS). The relative content of each component was determined by area normalization. The efficiency and chemical constituents of microwave assisted extraction were compared with that of traditional hydrodistillation. The results were as follows:1. Hydrodistillation extraction of volatile oil from Piper longum L. was carried out under different parameters of crush degree(A), soak time(B) and extraction time (C). The effect of extraction time (C) on the extraction rate of volatile oil was highly significant (P < 0.01), crush degree(A) and soak time(B) were significant (P < 0.05). The effect of crush degree(A) was greater than soak time(B).2. The optimum extraction process for volatile oil obtained by hydrodistillation was as follows: the proportion of material to solvent was 1:9, crush degree was 80 mesh, soak time was 4 hours, extraction time was 7 hours. The extration rate of volatile oil under the conditions was (0.597±0.015) mL·g-1.3. The equations of kinetic model for volatile oil obtained by hydrodistillation were as follows: V=2.06×(1-e-0.01103t) and ln(2.18-V)=-0.01044t+0.74828. The constant of two equations was respectively 0.01044 and 0.01103, VS was respectively 2.06 and 2.18 mL.4. Microwave assisted extraction of volatile oil from Piper longum L. was carried out under different parameters of crush degree (A), extraction time (B) and extraction power (C). The effect of extraction power (C) on the extraction rate of volatile oil was highly significant (P < 0.01), crush degree (A) and extraction time (B) were significant (P < 0.05). The effect of extraction time (B) was greater than crush degree (A). The proportion of material to solvent had not obvious effect on the extraction rate of volatile oil.5. The optimum extraction process for volatile oil obtained by microwave assisted extraction was as follows: the proportion of material to solvent was 1:5, crush degree was 60 mesh, extraction time was 30 seconds, extraction power was 325 watts. The extration rate of volatile oil under the conditions was (6.267±0.153) %.6. 25 compounds were identified in the volatile oil extracted by hydrodistillation by GC-MS, represented 97.091% of the total volatile oil. The major components of volatile oil were found to be Tridecane,δ-Elemene,α-Copaene 1H–cyclopropa [a] naphthalene,1a,2,3,5,6,7,7a,7b-octahydro-1,1,7,7a-tetramethyl-[1aR-[1a,alpha,7,alpha, 7a,alpha,7b,alpha]-,(±)-trans-α-Bergamotene, trans-Caryophyllene, (E)-α-Farnesene, (E)-β-Farnesene,(±)-α-Humulene,(R)-(-)-Curcumene,(±)-Germacrene,Aromadendrene, Pentadecane, (R)-(+)-β-Bisabolene,α-Caryophyllene, Caryophyllene oxide, Isolongifolene epoxide,α-Longifolene,α-Cadinol, 8-Heptadecene, 1-Heptadecene, Heptadecane,9-Nonadecene, 5-Nonadecene, Nonadecane.7. 20 compounds were identified in the volatile oil extracted by microwave assisted extraction by GC-MS, represented 96.518% of the total volatile oil. The major components of volatile oil were found to be Caryophyllene, 4,7,10,- cycloundecatriene,1,1,4,8-tetramethyl-cis,cis,cis-,GermacreneD,Tricylo[5,4,0,2,8,]undec-9-ene,2,6,8,9-tetramethyl-,2,6-Dimethyl-6-(4-methyl-3-pentenyl)-bicyclo[3.1.1]hept-2-ene,8-Heptadecene,1-Heptadecene,Heptadecane,Dodecahydropyrido[1,2-b]isoquinolin-6-one,5-Nonadecene,4-[(1-Carboxy-2-methylbutyl)amino]-2(1H)-pyrimidinone,(Z)-9,17-Octadecadienal,1-Methyl-cyclodecene,2-Diazo-2,3-dihydro-3-methyl-1H-inden-1-one,N-(2,5-Dimethoxyphemyl)-4-methoxy-benzamide,(1R)-1,7,7-Trimethyl-bicyclo[2.2.1]heptan-2-one,Decahydro-2-methyl-naphthalene,trans-Octahydro-2(1H)-naphthalenone,Tetradecahydro-1-methylphenanthrene, Piperine. 8. 25 compounds identified by hydrodistillation were including 13 terpenes (56.170%), 1 alcohol(0.977%), 2 terpene oxides(1.962%), 10 alkanes(25. 482%), 1 BTEX(1.078%). 20 compounds identified by microwave assisted extraction were including 5 terpenes(13.958%), 6 alkanes(37.280%), 2 acidamides(23.268%), 5 ketones(19.381%), 1 olefine aldehydes(0.345%), 1 condensed-nuclei aromaticses (3.374%).9. Comparative analysis found that hydrodistillation and microwave assisted extraction of volatile oil from Piper longum L. had discrepency in chemical components. We should choose appropriate extraction methods according to the main components of the volatile oil in actual production.
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