Chemical constituents of essential oils from aerial parts of Adenosma capitatum and Limnophila aromatica BJP

The essential oils were isolated by hydrodistillation from the aerial parts of Adenosma capitatum and Limnophila aromatica and were analyzed by gas chromatography mass spectrometry (GC-MS). Forty six and thirty components were identified, representing 98.8% and 99.3% of the total oils respectively. Oil of A. capitatum rich in limonene (24.74%), fenchone (21.59%) and 2-carene (17.64%). On the other hand, L. aromatica rich in Z-ocimene (39.21%), terpinolene (17.24%) and camphor (12.89%).


Plant material
Fresh aerial parts of A. capitatum and L. aromatica were collected from the plants grown in the campus of BCSIR Laboratory, Chittagong during June 2007. Two-voucher specimens (Y-463 and Y-464) were deposited in the herbarium of BCSIR Laboratory, Chittagong.

Extraction of essential oil
Both aerial parts were harvested and air-dried for about one week. The oils were obtained by hydrodistillation for 4 hours in a Clevenger-type apparatus (Clevenger, 1928;Bhuiyan et al., 2009). The oil yields (calculated per weight of dried material) were 1.1% for A. capitatum and 1.0% for L. aromatica. The oil samples were stored in air-tight containers after drying them over anhydrous sodium sulfate for GC-MS analysis.

GC-MS analysis
The essential oil from aerial parts of A. capitatum and L. aromatica were analyzed by GC-MS electron impact ionization (EI) method on GC-17A gas chromatograph (Shimadzu) coupled to a GC-MS QP 5050A mass spectrometer (Shimadzu); fused silica capillary column (30 m x 0.25 mm; 0.25 mm film thick-ness), coated with DB-5 (J & W); column temperature 100°C (2 min) to 250°C at the rate of 3°C/min; carrier gas, helium at constant pressure of 90 Kpa. Acquisition parameters full scan; scan range 40-350 amu.

Identification of the compounds
Compound identification was done by comparing the NIST library data of the peaks. Percentage composition was computed from GC peak areas on DB-5 column.

Results and Discussion
The essential oils from the aerial parts of A. capitatum and L. aromatica are presented with chemical constituents in Table I. A. capitatum oil contains 46 constituents of which the major is limonene (24.7%). Other notable constituents are fenchone (21.6%), 2carene (17.6%), Z-octahydro-7a-methyl-1H-indene-1one (14.3%), y-terpinene (3.0%), β-bisabolene (2.8%), fenchyl alcohol (2.1%), phytol (1.9%), α-caryophyllene (1.6%), caryophyllene (1.1%) and 2-cyclohexen-1-one, 3methyl-6-(1-methyle ethelidene (1.0%). According to GC-MS analysis under the conditions described above, Z-ocimene was detected as the main component (39.2%) of this essential oil of L. aromatica. The remaining constituents are terpinolene (17.2%), camphor (12.9%), b -myrcene (9.5%), limonene (3.8%), caryophyllene (3.1%), L-caryophyllene (2.9%), a-pinene (2.4%) and bfarnesene (1.4%). The study reveals that composition of two oils differs from the earlier reports published in the literature and may, therefore be treated as different chemotypes (Ji and Pu, 1985;Fujita and Yamashita, 1942;Tucker et al., 2002). On the basis of above fact it may be concluded that A. capitatum and L. aromatica, growing widely in Bangladesh, may be utilized as a source for the isolation of natural limonene and ocimene respectively. Limonene is common in cosmetic products, used in food manufacturing and some medicines, e.g., bitter alkaloids, as a flavoring; it is also used as botanical insecticide. It is added to cleaning products such as hand cleansers to give a lemon-orange fragrance. As it is combustible, limonene has also been considered as a biofuel. In perhaps its most exciting application, limonene is useful for recycling polystyrene. In the 1990s, researchers at Sony discovered that limonene dissolves polystyrene, which can be recovered after boiling off the limonene (Mann et al., 1994). Besides, it is worth noting that the oil of A. capitatum and L. aromatica have been reported to be used in folk medicine in the treatment of menstrual problems, rheumatism, wounds, dysentery, fever, elephantiasis and indigestion.

Conflict of Interest
Authors declare no conflict of interest Table I Constituents of essential oils from A. capitatum and L. aromatica SN. Name of constituents in A, capitatum % Name of constituents in L, aromatica %