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Indian Journal of Chemistry Vol. 42B, March 2003, pp. 641-647
Variations in the essential oil composition of Persea bombycina (King ex Hook. f.) Kost and its effect on mug a silkworm (Antheraea assama Ww) - A new report
S N Choudhury*
Plant Sciences and Ecology Division, Regional Research Laboratory , Jorhat -785006, Assam, India
and
Ingrid Vajczikova
Department of Chemistry, Institute of Chemical Technology , Prague, Czech Republic
Received 19 September 200 I .. accepted (revised) 20 November 2002
Persea bombycina, with the local name 'Som', is a primary food plant for the 'muga' silk worm (Antheraea assam a Ww). Hydrodistillation of the fresh green leaves of P. bombycina gives a clear and sweet scented oil in 0.02 to 0.054% (w/w) yield . The oil composition is investigated by GC and GC/MS. A total of 79 compounds have been identified . Substantial differences in the composition of the oils from 9 leaf samples are noticed. Aldehydes constitute a major portion of the oil (28 .0 to 53.2%) followed by acids (11.4 to 40.8%) and alcohols (7.4 to 14.8%). Dodecanal (3.1 to 25 .8%), decanal (2.4 to 25.8%), II-dodecenal (1.5 toI6.3%) and undecanal (1.3 to 9.5%) are present at extremely variable concentrations. Vari ations of (E)-nerolidol is quite conspicuous (0.5 % to 21.9%). Out of the two oxides, caryophyllene oxide is a major component (3.0 to 12.1 %). Experiments on rearing performances of muga silkworm on nine different collections of 'som', their most favoured host plant, reveal that growth of the worms are influenced unevenly by the different chemical constituents present in the essential oil. Correlation studies indicated that aldehyde per cent in the essential oil has positive influence on the growth of silkworm and cocoon quality , while increased ac id per cent in the oil is found to be detrimental for growth and cocoon quality.
Persea bombycina (King ex Hook. f.) Kost (Lauraceae)1 formerly named MachiLus bombycina King. is a medium size non-decidous tree found in the Assam valley in India up to an elevation of 500m (MSL)I.2. This tree, locally known as 'som', is perhaps a cultivated form of Machi/us gambLee or M. kurzii. Apart from Assam, its distribution extends to the Khasi and laintia Hills in India2 along the lower Himalaya, and as far as to the west of Nepal3. In Assam 'som' provides the primary food for 'muga' silk worms (Antheraea assama WW)4-6, which produce the golden silk very specific to the northeastern states of India and found nowhere else on the globe4.7-
11 . Lakhimpur district of Assam is one of the good
producers of 'muga' cocoons. Rearers use only 'som' plant as a main host for rearing of 'muga' worms. During the course of floristic survey of this district we encountered this species abundantly in natural stand. Organoleptic and olfectory tests made on the leaves at sources, revealed that their essential oil composition may differ from plant to plant.
It has been reported that 'som' plant have many varieties4, different morphotypes 12 and found different taste of leaves 13 but extensive work has not been done
on the chemical constituents of essential oil on this plantI4-16.
The role of inhibitors in host plant selection indicates that many different chemicals may be expected to have an inhibitory effect on feeding habits of different insects. Literature survey on essential oil and insect effect revealed that the terpenoids included upinene, B-pinene, limonene and eugenol contact of few insect was sufficient to evoke vitellogenesis and reproductive activi ty 17. Terpenoids present both in foliage and seeds of the cotton plant (Gossypium hersutum) is of importance in insect utilization of cotton varieties I8.19. On the other hand essential oils contain acyclic monoterpenes, such as geraniol, citronellal , citral and limonene have been identified as alarm defense subsrances in numerous insects2o.21. Repellent properties of aromatic hydrocarbons on insects have also been described22
-24. Aldehydes and ketones are
repellent at high concentrations to Erioschia brassicae25
, while the larvae of B. mori are attracted by the odour of n-butyl aldehyde. Decanoic acid reduces feeding on elm twigs by ScoLytus muLtiotriatui 6
,
while the pentatomids, thyanta sp and euschistus sp are repelled by the odour of methacrylic acid23. This
642 INDIAN J. CHEM., SEC B, MARCH 2003
indicating that essential oil constituents have prominent role on insect feeding and host selection.
The literature survey failed to uncover any published work on the existing chemotypic variations of the essential leaf oil in relation to rearing performance of 'muga' silk worms. Hence this paper is the first report on the searching out the chemical variations of the essential oil of leaves of P. bombycina and their effect on the growth and cocoon quality of muga silk worm.
Materials and Methods Nine 'som' plants were selected from Lakhimpur
district of Assam. These plants were demarcated as accession (A) number from 1 to 9. Air layering technique was adopting for collecting the plant samples in the month of April/May 1996. Six to eight air layerings were prepared in each selected plant. Four good layerings were planted in prepared pits at a spacing of 3.5 x 3.5 m. Plants height was maintained at 4.0 m.
Rearing of 'muga' worms was carried out during October-November CKatya' brood) of 1999. Each plant was covered by nylone net (3.5 x 3.5 x 4.0 m) over a bamboo frame made according to the size of the net. Di sease free lay ings(dfls) were first brushed into a bamboo tray and 100 numbers of newly emerged 1st instar larvae were transferred to each plant and allowed to complete larva l period. Matured larvae were collected from each plant and transfened to bamboo trays (one tray for each plant) filled up with dry leaves, after recording their weight. Cocoon characters such as average weight of cocoons, shell weight, silk ratio, effective rate of rearing were determined after 10 days of collection of matured larvae. Sericin and fibroin per cent were estimated from each shell27
. All the experiments were carried out at Regional Research Laboratory, JOI'hat, Assam during 1996-200 l.
Plant material. Fresh leaves were collected from each matured tree from the experimental farm of RRL, Jorhat, Assam.
Isolation of essential oils. Fresh leaves (300g) plant samples were hydrodisti lled in a clevengers apparatus, yielding 0.02 to 0.054% (w/w) of a clear oil. Qualitative and quantitative analysis
Gc. A Parkin-Elmer 8500 gas chromatograph equipped with a FID detector and a HP-l fused silica colimn (24 m x 0.32 mm, 0.17 11m film thickness) was used. The samples were injected in the sp lit mode, using pressure controlled helium as carrier gas at a
linear velocity of 30 cmls (at 60°C) Injector and detector temperatures were maintained at 250°C. The column oven temperature was programmed from 60°C (after 2 min) to 250°C at 4°C/min. The final temperature was held for 20 min. Peak areas and retention times were measured by electronic integration. The relative amounts of individual components are based on the peak areas obtained, without FlO response factor correction. Temperature programmed (linear) retention indices of the compounds were determined relative to n-alkanes.
GCIMS. Analyses were carried Ol,;.t on a Shimadzu GC-17A1GCMS-QP5000 system. A 25mxO.20 mm fused silica HP-l column, with a fi lm thickness of 0.33 Jlm, was employed. The column oven temperature was programmed from 60°C (after 3 min) to 300°C at 5°C/min. The injector and GC/MS interface temperatures were maintained at 280 and 300°C, respectively. Helium canier gas was pressure controlled to give a linear velocity of 44 cmls (at 60°C).Electron ionization mass spectra were acquired over the mass range 10-400 Da at a rate of 2/s.
Component identification. The constituents of the oils identified by matching their 70 cY mass spectra and linear temperature programmed retention indices with reference libraries28
.37
.
Results and Discussion Nine plants were selected at the source using or
ganoleptic and smearing smell of leaf test and essential oil compositions were further confirmed. Detailed GC and GCrMS analysis indicated that the oil was a complex mi xture consisting of more than 79 compounds. The volatile compounds indi ~ated in the oil are li sted in Table I.
The leaf oil was found to be very rich in aldehyde, constituted by twelve compounds. Total aldehyde percentage in the oil of different 'SO;11' plant varied significantly. The minimum (28.0%) was recorded in A9 whereas this percentage went up to 53.2% in case of AS. Detailed scrutiny of the Table I revealed that decanal itself contributed 25.8% out of 50.7% of total aldehyde per cent in A6. On the other hand this reduced to only 2.4% in A4. Dodecanal was another dominating constituents in AS (25.8 %), A7 (25.6%), A3 (23.3%), A8 (18.6%), and A4 (17 .2%). Choudhury and Leclercq reported higher percentage of dodecanal in the leaf of this plant from Jorhat district of Assaml 4. But the same constituent was found onl y 3. 1 % and 5.8% in A9 and A2 respectively. 11-dodecenal was found in varied percentages ( l.5 to 16.3).
CHOUDHURY et al.: ESSENTIAL COMPOSITION OF PERSEA BOMBYCINA 643
Table 1-Chemical composition of the leaf oils of Persea bombycina from Lakhimpur district of Assam, India
Compd Sesquiterpene hydrocarbons
a-copaene
~-caryophyllene
aromadendrene humulene
~-selinene
a-selinene
8-cadinene
Sesquiterpene alcohols
Elemol (E)-nerolidol caryophyllene alcohol globulol viridiflorol T-cadinol T-muurolol
~-eudesmol
selin-II-en-4 -01
a-cadinol
a-bisabolol (E,E)-farnesol
Aldehydes
heptanal octanal nonanal
a-campholenal 9-decenal decanal 10-undecenal undecanal II-dodecenal dodecanal 12-tridecenal tetradecanal
Esters
isobornyl acetate octyl decanoate nonyl decanoate decyl decanoate undecyl decanoate decyl II-dodecenoate decy l dodecanoate und.:cy I II-dodecenoate undecyl dodecanoate dodecy I I 1-dodecenoate dodecyl dodecanoate
R.I
1370
1411
1431 1444 1476 1486
1510
1530 1547 1555 1566 1574 1621 1623 1628
1629 1632
1664
1700
876 980 1082 1099
1174 1184 1275 1286 1378 1388 1480 1593
1265 1963 2061 2160 2259 2340 2358 2439 2450 2538 2550
Al
t
0.2 2.3
2.5
1.9
0.4 0.5
0.6 0.9
4.3
0.3 0.2 2.1
0.2 3.7 3.4 3.9
10.8 10.8 0.6 0.3
36.3
0.5
0.1
0.1 0.1
0.8
A2
0.9
t
0.2
1.1
21.9
1.0 0.5
0.1 1.4
0.5 25.4
0.1 0.1 5.3
12.0 0.4 1.6 4.0 5.8
0.2 29.5
0.8 t
0.1 t
0.1
0.1
0.1
1.2
A3
0.3
0.3
1.0
0.3 0.1
0.1 0.6
0.3 2.4
t
0.1 2.1
0.1 4.0 1.5 9.5 3.1
23.3
0.3 44.0
0.4
t
0.1 0.2 0. 1 0.1
t
0.4
t
1.3
A4
0.5
0.5
0.7 1.0
0.3 0.4
0.6 0.8
0.2 4.0
0.2 0.6
0.1 2.4 2.5 4.5
14.1 17.2 0.5 0.4
42.5
0.2
t
t
0.1 0.1
t 0.2 0.2
0.8
FID A5
0.3
1.1
0.9
2.3
1.5 1.6 1.4
0.7 0.3
1.0
0.3 6.8
0.1 0.5
0.1 3.8 2.2 4.3
16.3 25 .8
t
0.1 53.2
0.2
0.1
0.1 0.1
0.5
A6
0.6
0.1 t
0.4
0.1
1.2
0.2 5.3 0.1
25 .8 l.l 1.3 8.2 8.6 0.1
t
50.7
0.4
0.2 0.1
0.7
A7
1.1
1.1
2.0
0.9 0.1
0.7
3.7
1.7
3.3 0.4 5.9 4.2
25 .6 t
0.1 41.2
0.2
t
0.1 0.1
0.1 0.3
0.1 0.9
A8
0.1
0.3
0.4
0.4 l.l 3.9 0.6
5.9 1.4 4.8 2.4
18.6 0.6
39.7
0.2
0.2
A9
0.1
0.1
0.5 0.5 1.3
2.3
0.1 0.2
10.2
9.7 1.0 1.7 1.5 3.1 0.1 0.1
28.0
0.2 0.6 0.2 0.5
1.3 (-Contd)
644 INDIAN 1. CHEM., SEC B, MARCH 2003
Table I - Chemical composilion of Ihe leaf oils of Persea bombycina from Lakhimpur district of Assam, India (-Contc£)
Compd R.I FlO Sesquiterpene hydrocarbons AI A2 A3 A4 A5 A6 A7 A8 A9
Hydrocarbons
oclane 800 I 0.3 0.1 I 1.5 0.1 0.4 nonane 900 0.3 1.2 0.3 0.1 0.1 2.6 0.2 0.3 0.8 I-decene 988 0.4 0.1 t 0.1 0.4 0.7 0.4 decane 1000 0.3 0.1 0.6 0 .3 0.2 0.5 0 .3 p-cymene 1010 0.5 0.1 t I t I-undecene 1089 1.2 0.2 0.3 0 .5 0.6 1.0 0.3 0 .2 0 .2 undecane 1100 1.4 0.5 1.8 0.8 1.1 1.3 1.4 0.5 0.2 I-undecyne 111 2 tridecane 1300 I drima-7,9 (II)-diene 1460 0.5 heplacosane 2700 0.1 t I 0. 1 0.1 0.1 nonacosane 2900 0.1 0.1 0.2 t 0.1 I
4.3 2.5 3.2 2.01 2.6 6.8 2.6 2.1 2.1
Alcohols
I-heplanol 953 0.4 Isoborneal 11 35 t 0.1 I-nonanol 1158 1.3 5.3 1.3 0.5 0.4 4.9 1.4 2.7 6.5 terpinen-4-o1 1169 1.1 0.2 9-decen-l-ol 1246 I I I
I-decanol 1256 I 0.1 0.2 0.2 0.1 10-undecen-I-ol 1347 4.8 0.4 0.9 2.1 1.5 0.7 0 .7 1.0 0.6 I-undecanol 1358 5.8 2.0 6.9 4.0 3.4 1.1 5.6 6.6 3.0 I-alkano l 1501 1.8 1.2 3.0 2.2 0.4 2.0 4.1 0 .2 Irans-phYlol 2097 I 0.1 0.3 0.2 0.4 I 0.3
13.7 7.9 10.8 10.n 9.1 7.4 10.0 14.8 10.3
Oxides
caryophyllcne oxide 1562 3.3 3.4 6.2 12.1 3.3 5.1 8.0 3.0 3.0 humulene 1,2-epox ide 1588 1.9 0.6 I 1.8 1.0
3.3 5.3 6.8 12.1 5.1 5.1 9.0 3.0 3.0
Acids
oClanoic (capry lic) acid 1165
nonanoic acid 1259 I 0.1 I I
dccanoic (capric) ac id 1362 0 .9 2.7 1.1 1.4 0.3 9.6 2.0 5.9 32.8
I O-undecenoic acid 1445 0.4 0.6 1.1 t 0 .2 I 0.2 0.8
undecanoic acid 1458 0.4 1.0 1.3 1.2 0.4 0.1 0. 1 1.4
II-dodecenoic ac id 1545 6.0 1.9 I 2.7 3.0 2.9 0.1 6.5 2.0
dodecanoic (lauric) acid 1550 7.1 4.7 14.5 9.3 7.1 2.9 11.7 12.1 5.0
12-lridecenoic acid 1645 0.3 0.3 0.4
tridecanoic acid 1650 0.1 0. 1
tctradecanoic (myristic) acid 1751 0.2 0.2 0.3 0.3
hexadecanoic (pa lmi tic) acid 1940 0.1 0.1 0.2 0.2 I 0.2
15.4 11.4 18.9 14.9' 11.6 15.5 13.9 26.1 40.8
Ketone
2-t ridecanone 1478 0.3 0.6
Terpene
a-pincne 928 0.4 0.2 0.1
CHOUDHURY el aL.: ESSENTIAL COMPOSITION OF PERSEA BOMBYCINA 645
Heptanal, octanal, a-campholenal, 9-decenal, 10-undecenal, 12-tridecenal and tetradecanal were appeared as minor constituents in the leaf oils.
Total alcohol of each oil sample contributed a major percentage of the bulk of the oi l but significant variation existed among the percentages. Maximum percentage was recorded in A8 (14.8%). This percentage was drastically reduced to 7.4% in A6. 1-Undecanol was found as a major indi vidual compound in A3 (6.9%), A8 (6.6%), Al (5.8%) and A7 (5.6%). The second dominating compound, I-nonanol was found 6.5% and 5.3% in A 9 and A2 respectively.
Sesquiterpene alcohol was found to be extremely variable in 'som' leaf oil. Total 25.4% of sesquiterpene alcohol was detected in A2, whereas this was only 0.4% in case of A8. Considering the individual component, (E)-nerolidol was also recorded highest in A2 (21.9%) same chemical was found only 0 .5% in A9. The rest of the compounds occured in amounts less than 1.0% except for caryophyllene alcohol (1.6%), a-cadinol (1.4%) and globulol (1.4%).
The bulk of the leaf oil of 9 samples comprised ~f 12 hydrocarbons. Maximum total percentage (6.8) was recorded in A6 and lowest was only 2.0% in A4. None of the individual compounds amounted to more than l.2% except octane and undecane.
Sesquiterpene hydrocarbon occupied comperatively less percentage in the bulk of the oil. The variations of total sesquiterpene hydrocarbon was 0.1 % (A9) to 2.5% (A 1).
Acid percentage in the oil was quite high in all the samples, although there was a marked fluctuation in percentage. A9 contained highest percentage of acid (40.8%) of the bulk of the oil followed by 26.1 % in A8. It reduced to 11.4% in A2.
Eleven ester compounds have been detected from 9 leaf samples. But its contribution in the bulk of the oil remained only 1.3%.
Oxide percentage showed remarkable variation from 3.0% (A9) to 12.1 % (A4) . Caryophyllene oxide was a major compound in A4 (12.1 %) followed by A7 (8.0%), A3 (6.2%) and A6 (5.1 %). 2-Tridecanone was found in a very small quantities in Al (0.3%) and A 7 (0.6%). a-Pinene was detected only in three leaf samples and the percentage was less than 0.5.
A considerable variation in weight of individual muga larvae was found to exist while fed on nine 'som' plant (leaf) collected from only one district of Asssam (Table II). The plants having high aldehyde per cent in their oils produced healthy worms (14.0 to 14.3g), in less larval duration, with greater cocoon weight (6.0 to 6.2g), higher shell weight (0.65 to 0.67 g) and maximum ERR% (30.9 to 3l.3). This suggested that the aldehyde per cent in the leaf oil is beneficial for the muga worm. Ishikawa and Hirao,196538
. reported that larvae of B. mori are attracted by aldehyde at low concentrations while being repelled at high concentration. On the contrary the affinity of A. assama towards aldehydic compounds was found to increase with the increased concentration of the component. Acceptability and repellent character of different insectes on same chemicales at different concentrations have been well mentioned24
.39.4o. Fibroin, the filament forming true silk was also enhanced at higher aldehyde per cent. Strong positive correlation effect between aldehyde per cet in oil and larval weight (r=0.939), cocoon weight (r=0.855), shell weight (r=0.976), ERR% (r=0.665) and fibroin per cent (r = 0.71) also support this view (Table III). In contrast sericin per cent of the silk was low at higher aldehyde in oil. A negative correlation was recorded between the aldehyde per cent and sericin (r = -0.619), indicating that higher aldehyde per cent might have detrimental effect for the production of sericin (Table III).
Table II -Larval and cocoon characters of 'muga' silkworm (A. assama) as affected by major essential oi l constitu-ents of 'Som' (P. bombycina) collected from one district of Assam
Accession number of P.bombyc ina Elants collected from LakhimEur district of Assam Characters I 2 3 4 5 6 7 8 9
Mean larval wt (g) 12.00 12.00 13.50 13.70 14.30 14.00 13.60 12.80 11.60 Rearing period(days) 30.00 29.00 29.00 28.00 27.00 27.00 28.00 29.00 32.00 Mean cocoon wt (g) 5.00 4.60 5.10 5.70 6.20 6.00 5.80 5.60 5.00 Shell wt (g) 0.52 0.55 0.60 0.63 0.67 0.65 0.63 0.57 0.47 Silk ratio (0/0 ) 10.40 11.90 11.70 11.00 10.80 10.80 10.80 10.20 9.40 ERR (0/0 ) 30.8 22.9 24.3 25.5 31.3 30.9 27.3 22.6 18.3 Sericin (0/0 ) 21.80 18.40 16.40 19.90 16.00 16.10 17.00 21.40 22.20 Fibroin (0/0 ) 78.20 81.60 83.60 80.10 84.00 83.90 83.00 78.60 77.80
646 INDIAN 1. CHEM., SEC B, MARC H 2003
Table III - Showing the corre lation co-efficient values (r) between larva and cocoon qualities of muga silkworm (A. assama)
and essenti a l o il compos iti ons of P. bombycina
C harac ters r va lues
Aldehyde% and larva l WI. 0.939*
Aldehyde% and cocoon wI. 0 .855*
Aldehyde% and she ll wI. 0.976*
Aldehyde% and ER R% 0.665
Aldehyde% and seric in% -0.6 19
Aldehyde% and fibroin % 0 .7 10
Acid% and la rva l wI. -0.607
Acid% and cocoon wI. -0.270
Acid% and shell wI. -0.684
Acid% and ERR % -0.948*
Acid% and sericin % 0.62 1
Acid% and fibroin % -0.62 1
Acid content in the essential oil found to have negative effect on the yield and cocoon qua lity characters of 'muga' silk (Table II). Detrimental effect of acid on insect feeding was mentioned by earlier workers23
.26
. Significant negative correlation between
acid per cent in oil and larval weight (r = - 0.607),
shell weight (r= - 0 .684), ERR% (r=-0.948) and fibroin per cent (r =-0.621) confirm this findings (Table III).
Acknowledgement
The authors are grateful to North Eastern Council, Shillong, for providing financial help in conducting the investigation. We also thank Director, RRL, Jorhat fo r providing us the facilities to conduct the experiment. The authors are also grateful to (Late) Dr P A Leclercq, the then Scientist of Laboratory of Instrumental Analysis, Department of Chemical Engineering, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands for quantitative analys is of oi l samples.
References Bennet S S R, Name changes in flowering plants of India and adjacent regions (Triseas Publishers, Dehra Dun , India), 1987.
2 Kanjilal U N, Kanji la l P C, De R N & Das A, Flora of Assam (Periodica l Expert Book Agency, Delhi, India), 2nd Reprint , 1992, p. 46.
3 Hooker J D, Flora of British India, Vol. 5 (Willi am C lowes and Sons, London , Eng land), 1885, p. 859 .
4 Choudhury S N , Mllga Silk Industry, (Direc torate of Sericullure and weav iJlg, Assam, Indi a), 1981 , p. I.
5 Yadav G S & Goswami B C, Sericologia, 32, 1992,447.
6 Gogoi J K, Assomor Muga Shilpo(Assamese) (Jyoti Press, Assam, India), 1980, p. I .
7 Gogoi J K, A practical handbook of 'eri' and '11lIlga' cultllre (J yoti Press, Assam, India) 1984, p. 5.
8 Choudhury S N, Eri Muga Pat (Assamese) (Asom Vigyan Somity, Guwahati , Indi a), 1970, p. I .
9 Choudhury S N, Pro. Seminar on Ssericulture and Handloo/'/1 Industries, Assam, 1982, 39.
10 Bhara li N, Muga industries in Assam, Pro. Seminar on Sericulture and Handloom Industries, Assam , 1982, 3 1.
I I Talukdar J N , Pro. Selninar on Sericulture and Handloom Industries, Assam, 1982, 27.
12 Raj a R, Sengupta K, Das K, Dev nath M & Samson M V, Sericologia , 33, 1993, 109.
13 Bharali N N, Indian Silk, 10, 1971 , 5,
14 Choudhury S N & Leclercq P A, 1. Essell l. Oil Res., 7, 1995, 199
15 Choudhury S N, Ghosh A C , C houdhury M & Leclercq P A, J. Essel1l Oil Res., 9,1997, 177.
16 Hazarika R L, Baruah J N, Deka PC, Hazarika A K & Kataky J C, Inri. Peliumer, 38, 1994, 33.
17 Hendry L B, Wichmann J K, Hinderiang D M, Mumma R 0 & Anderson M E, Science , 188, 1975,59.
IS Maxwell F G , Jenkins J N & Parrott W L, J Econ EII I. 60, 1967, 1294.
19 Maxwell F G , Jenkin s J N & Parrott W L, Adv Agron , 24 , 1972, 187.
20 Weatherston J & Percy J E , Chemical conlrolling insecl behavior, edited by M Beroza (Academic Press, New York), 1970.
2 1 Wil son EO & Regnier F F, Amer. Nat, 105, 1971 , 279.
22 Norri s D M , Ann. Enl. Soc.Am.63, 1970, 476.
23 EisnerT, Science, 146, 1964, 13 18.
24 Khali fa A, Salama H S, Azmy N & E I-Sharaby , J In seCT Physiol, 20, 1974, 67.
25 Cocker T H & Finch S, Symp. R. Entomol Soc London, 6, 1973, 11 9.
26 Touhey J G & Bray D F, J Econ Enl, 54, 1961 ,293.
27 Ahmed R Z, Choudhury S N & Bhattacharyya P R, Sericologia, 3S, 1998,699.
28 Anon. The SadTler STandard Gas Chromatography ReTenTion Illdex Library , Bio-Rad Labora tory, Philadelphia, PA , USA, 1986.
29 Davies N W , J Ch romaTOgr, 503, 1990, I .
30 Sandra P & Bicchi C, Capill ary, Gas ChromaTography in EssenTial Oil Analysis (Huthing, Heidelberg, Germany), 1987.
3 1 Masada Y, Analysis of Essential Oils by Gas ChromaTography and Mass Spectrolnetry (Wiley, New York), 1967.
32 Libbey L M , J EssenT. Oil Res., 3, 199 1, 193.
33 Ramaswami S K, Bri scese P, Gargiuii o R J & Geldern T, Sesquitrrpene hydrocarbons: from mass confusion TO orderly line-up. In: Flovours and fragra nces: A world persoec ti ve, edited by, B M Lawrence, B D Mookherjee & B J Willi s (Elsevie r Sci. Publ., Amsterdam, The Netherlands), 1988 .
34 Adams R P, IdentificaTion of essellTial oil componenTs by gas chromaTOgraphy/ mass speCTroscopy (A ll ured Publ. Corp., Carol Stream, II. USA), 1995.
CHOUDHURY er al.: ESSENTIAL COMPOSITION OF PERSEA BOMBYCINA 647
35 Henncbcrg 0 , Weimann B & loppek , Mass spectrometry library search system Masslab, version 7.4 (for Ultrix), MaxPlanck-Institute fur Kohlenforschung, Mulheim/Ruh, Germany, 1990.
Using MassLib the following data bases were searched:
a) McLafferty F W & Stauffer, Th e Wiley/NBS Registry of Mass Spectral Dara, 4th Edn, (Wiley-Interscience, New York), 1988. b) Henneberg 0 , Weimann B & loppek W, MPI Library of Mass Spectral Dara, Max- Planck Instiut fur Kohlenforschung, Mulheim/Ruhr, Germany, 1994. c) Brauw M C ten Noever de, Bouwman J, Tas A C & Vos G F L, COll/pilarion of mass spectra of volarile compounds in food, TNO-HVV -CSIA, Zeist, The Netherlands, 1988. d) Posthumus M A & Teuni s C J, WAU Library of Mass Soecrral of Narural Products, Wageningen Agricultural Uni-
versity, Wageningen, The Netherlands, 1977.
e) Leclercq P A & Snijders H M, EUT Library of EL Mass Spectra, Edindhoven University of Technology, Eindhoven, The Netherland, 1998.
36 National Institute of Standards and Technology, PCV Version of the NIST/NIH mass spectral darabase, version 4.5 , U.S. Department of Commerce, Gaitherburg, MD, USA, 1994.
37 Mclafferty F W & Stauffer 0 B, Mass Specrromerry LibrGlY Search Sysrem Bench Top/PBM, version 3.0, Pali sad Co. , Newfield, 1993, Using Bench Top/PBM the followin g database was searched: McLafferty F W & Stauffer 0 B, The Wiley/Mbs Regi stry of Mass Spectral Data, 5th edition, Wiley and Sones, New York, 1991.
38 Ishikawa S & Hirao T, Bull Seric. Exp. Stn , 20, 1965, 21. 39 Long W H, Fm. Chern, 125, 1962, 22.
40 Nayer J K & Fraenkel, J Insect Phy, 8, 1962, 505.