INTRODUCTION:

Suspension is a coarse dispersion of fine insoluble solid particles dispersed in liquid medium. To overcome the problem of inadequate dispersion of fine particles in vehicle, settling of dispersed particles in suspensions, suspending agents are used¹ A pharmaceutical suspension, like other disperse systems, is thermodynamically unstable, thus, making it necessary to include in the dosage form, a stabilizer or suspending agent which reduces the rate of settling and permits easy redispersion of any settled particulate matter both by protective colloidal action and by increasing the consistency of the suspending medium^2-3. Suspending agents are (i) inorganic materials, (ii) synthetic compounds, or (iii) polysaccharides. Natural gums belong to the latter group⁴.Mucilages are naturally occurring polysaccharides, chemically cross-linked polymer of galactouronic acid. They are well known for their medicinal properties and presently applicable widely in pharmaceutical, Ayurvedic, cosmetic and textile industries as emulsifying, suspending, binding, stabilizer, fixative properties. Additives play an important role in pharmaceutical finished preparations, such as lotion, suspension, syrup, ointment, tabletetc.^5-8

Recent trends toward the use of natural, vegetable and non-toxic product urges the demand to replace the synthetic additives. Vegetable additives provide best solution to the current problems of toxicity, incompatibility, feasibility of synthetic additives. With the increase in demand for natural gums, it has been necessary to explore the newer sources of gums to meet the industrial demands. India, due to its geographical and environmental positioning has traditionally been a good source for such products among the Asian countries.⁹ Hence the present work was undertaken to evaluate suspending properties of combined seed mucilage of Ocimum basilicum, Plantago ovata and Lepodium sativum, with the aim to avoid the problems of synthetic additives.

EXPERIMENTAL WORK:

Isolation of mucilage:

25g of each plant seeds were soaked in distilled water (500ml) at room temperature for 12hr. The resulting mass was stirred at about 100 rpm for 1hr. and strained through muslin cloth. To the filtrate, acetone was added until precipitation was complete. The precipitated mucilage was filtered through muslin cloth and mucilaginous residue was spread on glass plates and dried at 40°C for 24h¹⁰. The flakes are then powdered and passed through mesh 40 for experimental use.

Evaluation of toxicity:

To determine the safety levels of extracted mucilages, acute toxicity studies were carried out according to Knudsen and Curtis¹¹. The animals used in the study were sanctioned by the Institutional Animal Ethics Committee, Bharati Vidyapeeth College of Pharmacy, Kolhapur. Swiss mice weighing 20-25g of either sex aged 8-10 w were fasted for 18h and used.

Acute toxicity studies: In acute toxicity studies first minimum dose from 2-10mg/kg body weight of combined seed mucilage in distilled water was tried orally using six animals in each group and observed for 24 hrs. Since no toxicity and mortality was observed, then a dose of 250mg/kg was administered orally to 12 mice with an additional 6 kept as control. Then they were observed for motor reflexes for 48 hrs. Again no mortality was observed and behavioral pattern was unaffected, further studies were carried out using different sets of animals (12 tests and 6 controls) where a dose of 500mg/kg was administered and the animals were observed for 72h. Similar observations were found using dose of 500mg/kg of combined mucilages of Ocimum basilicum, Plantago ovata and Lepodium sativum in 1:1:1 proportion.

Preparation of zinc oxide suspension:

Zinc oxide (Merck) sieved through 100 # was used to yield a 20% w/v suspension in distilled water using tragacanth (LDH), Sodium cmc (Loba) and individual seed mucilage and their combined form (1:1:1). Using each suspending agent, suspensions were prepared with four concentrations (1.0, 1.5, 2.0 and 2.5% w/v). For making the suspensions, zinc oxide first levigated with glycerin (1:1). Then weighed amount of these suspending agents were added and triturated and finally volume was made up with distilled water. Benzoic acid (0.1% w/v) was added as a preservative. All the suspensions were deflocculated. To determine the degree of flocculation, flocculated suspensions were also prepared using a flocculating agent, potassium dihydrogen phosphate (0.004 moles).

Rate of separation:

The rate of separation of suspension were studied by keeping 50ml portion of each suspension in stopperd measuring cylinder and stored undisturbed at room temperature. The separation of clear liquid was noted at intervals of 5d up to 45d.The separation ratio was calculated using the formula Hs/Ho, where Hs is the height of clear liquid and Ho is original height of sample¹².

Degree of flocculation:

The degree of flocculation¹³ was determined from following equation,

β = F/Fα

Where, F is ultimate sedimentation volume in the flocculated suspension and Fα is ultimate sedimentation volume in deflocculated suspension.

Redispersion:

Fixed volume (50 ml) of each suspension was kept in calibrated tube which were then stored at room temperature for various time intervals (5, 10 45 d). At regular interval of 5 d, one tube was removed and shaken vigorously to redistribute the sediment and presence of deposit if any, was recorded.

RESULT AND DISCUSSION:

Studies for acute toxicity of combined mucilages indicated no manifestation of toxic syndrome in experimental animals (Table-1 and 2). The combined mucilage from Ocimum basilicum, Plantago ovata and Lepodium sativum were found to be superior to tragacanth, bentonite and comparable to sodium CMC at 1, 1.5,and 2% concentrations while at 2.5% it has shown better suspending property than sodium CMC (Table-3a and 3b, Fig-1). Comparison of β values of suspension prepared with sodium CMC and combined seed mucilage shows higher values at 2 and 2.5% w/v levels (Table-4, Fig-2). Thus, the combined effect of mucilages will be a good source of pharmaceutical adjuvant specifically as a suspending agent.

Table-1. Acute toxicity studies of combined seed mucilage (1:1:1)*:

Group	Dose	Combined seed mucilage Toxicity (24 h)
Group	Dose	Motor reflexes	Behavior pattern
01	02mg	Normal	Normal
02	04mg	Normal	Normal
03	06mg	Normal	Normal
04	08mg	Normal	Normal
05	10mg	Normal	Normal
control	--	Normal	Normal

*Combined seed mucilage of Ocimum basilicum, Plantago ovata and Lepodium sativum,

Table-2. Acute toxicity studies of seed mucilages (dose 250mg/kg):

Group	Animals used	Toxicity (48h)
		Motor reflexes	Behavior pattern
		Combined seed mucilage	Combined seed mucilage
Test	12	Normal motor reflexes	Slightly more active
Control	06	Normal	Normal

Fig 1: Rate of separation of combined seed mucilage

Table-3a. Rate of separation:

Sr. no.	Time (days)	H_S/H_O
		Tragacanth				Bentonite
		1%	1.5%	2%	2.5%	1%	1.5%	2%	2.5%
01	05	0.25	0.10	0.07	0.05	0.45	0.25	0.15	0.10
02	10	0.40	0.37	0.34	0.29	0.55	0.36	0.26	0.21
03	15	0.57	0.50	0.43	0.36	0.59	0.43	0.32	0.28
04	20	0.63	0.57	0.51	0.45	0.63	0.48	0.37	0.33
05	25	0.64	0.57	0.52	0.47	0.65	0.51	0.40	0.38
06	30	0.65	0.57	0.53	0.49	0.67	0.51	0.42	0.40
07	35	0.65	0.57	0.53	0.49	0.67	0.51	0.42	0.41
08	40	0.66	0.57	0.53	0.49	0.67	0.51	0.42	0.41
09	45	0.66	0.57	0.53	0.49	0.67	0.51	0.42	0.41

Table -3b. Rate of separation:

Sr. no.	Time	H_S/H_O
		Sod. CMC				Combined mucilage
		1%	1.5%	2%	2.5%	1%	1.5%	2%	2.5%
01	05	0.10	0.04	0.02	0.01	0.08	0.04	0.02	0.00
02	10	0.18	0.12	0.08	0.07	0.16	0.13	0.10	0.01
03	15	0.22	0.16	0.12	0.11	0.20	0.16	0.13	0.08
04	20	0.24	0.18	0.18	0.17	0.22	0.19	0.16	0.11
05	25	0.26	0.22	0.22	0.20	0.24	0.22	0.20	0.15
06	30	0.28	0.24	0.24	0.23	0.26	0.26	0.23	0.18
07	35	0.31	0.27	0.26	0.25	0.29	0.26	0.23	0.19
08	40	0.31	0.27	0.26	0.25	0.29	0.26	0.23	0.19
09	45	0.31	0.27	0.26	0.25	0.29	0.26	0.23	0.19

Table-4. Degree of flocculation (β) of various suspending agents^a.

Sr. no.	Suspending agent	Concentration (%w/v)	Degree of flocculation (β)²
1	Bentonite	1.0	0.68 ± 0.01
		1.5	0.92 ± 0.08
		2.0	1.16 ± 0.12
		2.5	1.56 ± 0.15
2	Tragacanth	1.0	0.78 ± 0.00
		1.5	1.82 ± 0.00
		2.0	2.64 ± 0.09
		2.5	3.40 ± 0.16
3	Sod. CMC	1.0	2.89 ± 0.11
		1.5	3.54 ± 0.15
		2.0	3.89 ± 0.10
		2.5	4.06 ± 0.13
4	Combined seed mucilage	1.0	2.91± 0.10
		1.5	3.56 ± 0.12
		2.0	3.98 ± 0.15
		2.5	4.12 ± 0.15

^aData was recorder after 45 d keeping at room temperature (25⁰C). ²Data represents as the mean ± SD of three readings.

Fig 2: Degree of flocculation (β) of various suspending agents

CONCLUSION:

The extracted combined seed of mucilage of Ocimum basilicum, Plantago ovata and Lepodium sativum will be a good source of pharmaceutical adjuvant exclusively as a suspending agent even at lower concentration (2.5%). It has also shown better suspending property without any toxicity than much favored agents used in pharmaceutical industries. The binding and emulsifying properties of combined seed mucilage are being studied.

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Received on 02.10.2010 Modified on 08.11.2010

Research J. Pharm. and Tech. 4(4): April 2011; Page 555-557