The chemistry and pharmacology of the essential oil from the leaves of Hyptis suaveolens (L) Point

C.K. MUTAYABARWA,* S.C. CHHABRA,*
G.M.P. MWALUKO,** J. FULGENCE,** and W. MSANGI**

*Traditional Medicine Research Unit
** Department of Pharmacology
Muhimbili Medical Centre
P.O. Box 65001
Dar es Salaam, Tanzania

Introduction

The use of indigenous plants for medical purposes is one of the greatest heritage our community must be proud of and preserve. Through trial and error, our ancestors collected the knowledge of plants which they used for various reasons. They developed medicines to cure ailments, arrow poisons to paralyse animals and birds, made colours, for decorating ornaments and clothes, cosmetics, perfumes and made preservatives. The proper knowledge of the plants which are useful and authentic is left with old men and women who are just ending their life span, and a few are left. Unlike in other continents, the African herbal knowledge is non-documented, which is resulting into a gradual extinction of traditional methods of healing using herbs and natural salts. We are hereby calling scientists of all professions to come to the rescue of our culture which is useful to none, except ourselves. We won't go in detail mentioning specific drugs in the pharmaceutical shelves which are of plant origin, but it is estimated to be about 60%. We believe that the duty of experts involved in traditional medicine research is to provide scientific basis of the practices of our herbalists aimed at upgrading, improving or authenticating their practices, pointing out without fear, the bogus medicinemen and fake traditional healers and assure medical practitioners that, the drugs made from indigenous plants are as good as modern ones. Thus by doing this the scientific community shall be making a very useful contribution to therapeutic innovation in primary health care in Africa.

We shall now present our research results on one of the medicinal plants commonly found in Tanzania which is called Hyptis suaveolens.

The plant is a herb of about 60 - 90cm tall. It is widely distributed all over Tanzania (Watt and Brandwijk 1969) and it is known by different vernacular names; e.g. Mvumbasi (Swahili), Mkamba (Chagga) and Mwatabazimu (Haya) etc. The plant is used by traditional healers to treat epilepsy, febrile, convulsions and abdominal pains (direct communication with healers). It is also reported to cure parasitic cutaneous diseases and fungal infections.

Chemical analysis of the plant led to the isolation of L-sabinene, d-limonene, fenchone, a-terpinene and felandrene (Mukherje et al. 1964), as well as several triterpenic acids, such as ursolic acid (Misra et al. 1983), diterpenoids, such as suaveolic acid and suaveolol (Misra et al. 1981).

We have extracted the volatile oil from the leaves of Hyptis suaveolens and investigated its chemical nature and then determined the antiepileptic activity of the extract in experimental animals.

Methods

Extraction of the volatile oil

The oil was extracted from fresh leaves by steam distillation using a Cleavenger apparatus. Then the extract was dried using dried sodium sulphate. The oil had a specific gravity of 0.6554 and specific rotation of +0.50°, in chloroform. Twelve normal alkanes C₉ to C₂₀ were used as internal standards. Results are reported in Table 3.

Screening for anticonvulsant activity

The anticonvulsant activity of the oil was investigated in white albino mice of the genus Thaillers, weighing 20 - 30 g. The experiment consisted of three parts:

(i) Establishing the working dose of metrazol (Table 1).

(ii) Establishing the optimum working dose of the essential oil (Table 2).

(iii) Screening for the anticonvulsant activity of the essential oil as compared to phenobarbitone (Table 4).

Table 1: Establishing a Safe Working Dose for Metrazol

Mouse	Weight(g)	Time to convulse (Sec)	Time to Death (Sec)
Gr. Ia
1	24	-	-
2	26	-	-
3	27	-	-
4	28	-	-
5	25	-	-
6	27	-	-
Gr. IIb
1	29	445	-
2	25	120	-
3	27	161	-
4	28	132	-
5	25	170	-
6	26	170	-
Gr.IIIc
1	27	108	180 min lethal dose
2	27	92	106
3	26	60	200
4	28	75	150
5	29	105	-
6	28	100	160

^aDose give = 50 mg/kg; ^bDose given = 60 mg/kg; ^cDose given = 70 mg/kg

Table 2: Establishment of the Safe Working Dose of the Essential Oil of Hyptis Suaveolens

Mouse	Dose of the Hyptis oil Ml/Kg.	Time to death (sec) and % mortality in brackets
Gr. I	1.0	700 (60)
Gr. II	0.9	3600 (10)
Gr. III	0.8	4800 (1)
Gr. IV	0.6	-
Gr. V	0.5	-
Gr. VI	0.4	-
Gr. VII	0.3	-
Gr. VIII	0.2	-
Gr. IX	0.1	-
Gr. X	0 (only archis oil)	-

*Average weight of the mice was 28 g.

Table 3. Identified Peaks With Retention Time, Kovat's Retention Indices, Area Percentage, and Identification

S. No.	Peak No (Min)	Retention (Time) Indices	Kovat’s retention	Percentage Identification composition
1.	14	14.259	916	0.026Eumene
2.	15	14.655	924	0.00915-methyl-3 heptanone
3.	17	15.531	939	1.6978Benzaldehyde
4.	18	16.238	952	0.0539 Camphene
5.	21	16.994	964	2.12952-Octanone
6.	22	17.226	968	0.0801Sabinene
7.	23	17.575	973	0.7877b-Pinene
8.	24	18.01	980	1.5211Octan-3-ol
9.	25	18.299	984	1.1144Myrcene
10.	26	19.485	1006	0.0711Phellandrene
11.	27	19.769	1006	1.0194Benzyl alcohol
12.	28	20.058	1011	1.00793-Carene
13.	29	20.298	1015	0.3210a-Terpinene
14.	30	20.474	1017	2.6766P-cumene
15.	35	24.02	1070	0.1067Methyl benzoate
16.	36	24.12	1071	0.1829Fenchone
17.	37	24.55	1077	9.9796Linolool oxide
18.	38	25.1	1084	0.6196Linalool
19.	41	26.69	1106	9.6622Fenchyl alcohol
20.	43	27.67	1120	0.0288Cresol
21.	44	28.31	1130	0.483Camphor
22.	45	28.71	1135	0.0223Benzyl acetate
23.	46	29.16	1142	0.0347Menthone
24.	47	30.01	1154	0.5535Borneol
25.	49	30.81	1164	0.626Menthol
26.	50	31.12	1168	0.7354Terpinene-4-ol
27.	51	31.82	1178	1.5883a-Terpeneol
28.	56	34.35	1121	0.0491Citronellol
29.	57	34.93	1220	0.0187Cinnamaldehyde
30.	58	35.56	1229	0.0018Piperitone
31.	59	35.95	1235	0.0065Geraniol
32.	60	36.23	1239	0.0054Linalyl acetate
33.	61	36.85	1247	0.0179Citral (trans)
34.	63	37.92	1262	0.0615Anethole
35.	65	38.55	1271	0.0020Bornyl acetate
36.	66	38.98	1276	0.0137Cinnamyl alcohol
37.	74	42.89	1332	0.0477Terpinyl acetate
38.	75	43.53	1341	0.2090Eugenol
39.	76	45.04	1363	0.0113Nerol acetate
40.	78	46.53	1398	0.0126Isoeugenol (cis)
41.	79	47.23	1398	0.1187a-Guaiene
42.	80	47.61	1398	0.0126b-Guaiene
43.	82	48.57	1413	0.0394 Longifelone
44.	83	48.95	1418	0.0245Isoeugenol (trans)
45.	84	49.59	1428	8.0610b-caryophyllene
46.	86	50.52	1443	0.0242b-Bulsesene
47.	87	50.86	1448	0.1643Aromadeodrene
48.	88	51.71	1461	0.5037Humulene
49.	89	52.23	1468	0.1324Alloaromadendrene
50.	90	52.86	1477	0.0244Guaia-3,7 diene
51.	92	53.8	1491	0.1424b-Bulnesene
52.	94	54.85	1507	0.0244a-Chigadmarene
53.	95	55.38	1515	0.1155Nerolidol (cis)
54.	99	57.61	1551	0.0820Nerolidol (trans)
55.	100	58.3	1562	0.0391Apitonene-1
56.	101	58.67	1568	0.0512Apitonene-2
57.	103	59.56	1582	0.4500Caryophyllene oxide
58.	114	65.59	1680	0.4990Farnesol (trans)
59.	116	67	1702	0.0308Farnesol (cis)

Table 4: Anticonvulsant Activity of Hyptis Oil as Compared to Phenobarbitone

Volatile oil 0.5 ml/kg body weight	= VO
Arachis oil added to 1.0 ml	= AO
Metrazol 70 mg/kg body weight	= Metrazol
Phenobarbitone 50m g/kg body weight	= (Pb)

-Ve Control AO + Metrazole			Test V.O. +MetrazoIe			+Ve control Pb +Metrazole
Mouse weight	Time to Conv.) (Min)	Time to Death (Min)	Mouse weight (g)	Time to conv. (Min)	Time to Death (Min)	Mouse weight (g)	Time to Conv. (Min)	Time to Death (Min)
A.
27	120	150	28	-	-	30	-	-
28	100	106	24	-	-	22	-	-
25	121	138	25	-	-	27	-	-
28	108	160	28	-	-	28	-	-
26	93	110	30	-	-	25	-	-
27	75	102	28	-	-	27	-	-
B.
25	100	145	25	-	-	25	-	-
25	75	132	29	-	-	28	-	-
28	82	102	22	-	-	27	-	-
29	61	121	27	-	-	26	-	-
25	99	150	26	-	-	29	-	-
26	102	200	25	-	-	25	-	-
C.
25	110	160	25	-	-	25	-	-
28	69	109	26	-	-	30	-	-
30	95	132	27	-	-	25	-	-
22	102	149	22	-	-	27	-	-
26	100	140	27	-	-	28	-	-
27	82	120	28	-	-	25	-	-

Metrazol (60 mg/kg body weight) is the maximum toxic dose which induced convulsions in mice with minimum mortality rate, whereas 70 mg/kg body weight is the minimum lethal dose causing 99% mortality of the mice. The volatile oil 0.5 ml/kg body weight injected intraperitoneally was safe to mice, but higher doses such as, 1 ml/kg body weight of the volatile oil caused 60% mortality; 0.9 ml/kg body weight caused 10% morality and 0.8 ml/kg body weight caused 1% mortality.

0.5 ml/kg body weight of the Hyptis oil gave 100% protection against metrazol (70 mg/kg) induced convulsions, which was equivalent to the protection offered by phenobarbitone (50 mg/kg).

Discussion

There has not been any report on the anticonvulsant activity of the volatile oil from the leaves of Hyptis suaveolens. The results of the present study show that the volatile oil offered protection against metrazol and induced epileptic convulsions. The results confirm the usage of the leaves by traditional healers in the management of epilepsy. The toxicity of the oil cannot be overlooked as it has high mortality in mice injected intraperitoneally in higher doses (above 0.5 ml/kg). However, since the oil has been used for a long time without any reported toxicity we would advise the traditional healers to continue administering the medicine on a first aid basis using natural methods.

References

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