INTRODUCTION:

Skin or the cutaneous layer is the external covering of the body and is part of the integumentary system, that protects the body from surrounding environment and acts as sensory organ¹. It is made up of three layers namely epidermis, dermis and hypodermis. Sunlight has three forms: infrared (heat/visible), visible light and ultraviolet. Ultraviolet light is classified into three categories: UVA (320 to 400nm) also known as black light causes tanning. UVB (290 to 320 nm) causes damage in the form of sunburn and UVC (100 to 290 nm) which is filtered out by the atmosphere and never reaches earth’s surface. It is the UVB that causes most of the problems related to sun exposure: like aging, wrinkles and cancer². The SPF of a sunscreen is a laboratory measure of the effectiveness of sunscreen. The higher the SPF, higher the protection offered by a sunscreen against UV-B. The SPF is the amount of UV radiation required to cause sunburn on skin with the the sunscreen with respect to the amount required without the sunscreen³. Aloe vera serves for numerous purposes. It is used both internally and externally for multiple functions.

It is widely used for treating various digestive and dermatological disorders. It acts as immunomodulator and is used for skin care applications⁴.

MATERIAL AND METHOD:

Materials:

Aloe vera freeze dried powder was obtained from Anjaneyulu herbals, Vijayawada. Sodium alginate, calcium chloride, bentonite, zinc oxide and calamine were purchased from S.D. fine- chem. Ltd, Mumbai. All Chemicals and solvents used in the study were of analytical reagent grade. Fresh distilled water was used.

Preparation of calamine lotion⁵:

Calamine lotion was formulated as per IP 1996. Sodium citrate was added to 70 ml of distilled water in a mortar to this accurately weighed Calamine, zinc oxide and bentonite were added and triturated well in one direction to form a paste. To the paste liquified phenol, glycerin were added and triturated. Finally made up the volume to require volume with remaining quantity of water and the lotion was transferred into clean and dry bottle.

Preparation of Conventional lotion⁶:

The conventional lotion was prepared by incorporating 200mg aloe gel directly into 100ml of calamine lotion IP.

Preparation of Novel lotion⁷:

Preparation of beads:

Beads were prepared by ionic gelation technique. Disperse 100 mg of Sodium alginate solution in 5 ml of distilled water add 20mg of freeze dried powder of aloe , mixed using magnetic stirrer ( Remi, India) for 5 min. This was then extruded via syringe (no-18) into 10% calcium chloride solution with gentle agitation at 37°C. The formed beads were allowed to stand for 5 min in the solution, separated by filtration through whattman filter paper.

Novel lotion was prepared by suspending beads equivalent to 200mg aloe gel in 100 ml of calamine lotion IP.

Freeze-Dried Aloe vera Gel Preparation:

The freeze dried powder was obtained from the market. Its ratio of AVG to lyophilized powder was 10:1. So quantity equivalent to 200mg of gel was weighed and suspended into 100ml of calamine lotion.

EVALUATION OF BEADS⁷:

Morphology of beads: The mean diameter of dried beads was measured using optical microscope.

Crushing strength: The beads of aloe gel were pressed over butter paper to observe the crushing of beads to access its handling during application of lotion.

EVALUATION OF LOTIONS:

Colour and P^H: Colour was observed with naked eye, to observe the compatibility with skin. P^H of lotions was determined by using pH meter.

Rheological studies:

Viscosity⁸: Viscosity of the lotions was determined by Brookfield viscometer.

Spreadability⁹: Spreadability of formulation was determined with the apparatus proposed andfabricated by Multimer et al.

Physical stability:

Sedimentation volume¹⁰: All the lotions were allowed to stand for 24hrs and sedimentation volume (F) was calculated by using standard formula.

F= Ultimate volume of the sediment

Initial volume of sediment

Redispersibility¹¹: Redispersibility of lotion was observed after 24hrs by its flocculation by shaking.

Freeze thaw method¹²: Stability testing was done by using freeze thaw cycling method. The temperature was altered every 24 hours between 25^°Cand -5^°C for two cycles and samples were observed for physical stability.

Creaming¹³: Creaming property for 5ml of each lotion was determined by keeping them at refrigerated temperature (-4ºc) for 24hrs and separation of solid and liquid phase were observed.

Effectiveness

Sensitivity of lotion: Six volunteers (20-25yrs), after applying the lotions on forearm for 20 minutes, observed for any irritation or edema formation.

Psychometric effect⁷: Lotion was applied twice a day once in morning (9.00a.m) and once in evening (5.00p.m) over five volunteers (20-22yrs) upto 7 days and observations were noted verbly for firmness, softness, smoothness and lusture of skin.

Sun protection factor determination:

In Vitro SPF determination¹⁴:

In Vitro SPF can be determined by modified spectral analysis method described by Mansur et al ¹⁴.

SPF=C.F.₂₅₅Σ³⁵⁰.EE(λ).Abs.(λ)

Where, CF=Correction factor, EE (λ) = Erythmogenic effect of radiation with wavelength λ, Abs. (λ) = spectrophotometric absorbance values of a solution of the preparation at λ.

In Vivo SPF determination:

Five volunteers (20-22 yrs) with their willingness were included in the study. A rubber sheet of the forearm length, with three circles of 2.5 cm diameter each was used to cover the forearm. Each volunteer applied 2 mg/cm² of lotions to volar forearm at separated area with the use of the rubber sheet as regulator. For universal spread of lotion, 5 standardised circular hand movements were used. Five volunteers were subjected to sun exposure following application of study lotions and the time taken for the appearance of primary outcome measures like development of erythema(redness) is noted.

SPF = The time required to produce erythema with protected area

The time required to produce erythema with unprotected area

RESULTS AND DISCUSSION:

The prepared conventional lotion and freeze dried aloe powder lotion were evaluated for physical, rheological and stability parameters. The p^Hof the lotion indicates that they were slightly basic (Table 1), compatible with the skin. All the formulations were pink in colour. The rheological properties like viscosity and spreadability values indicate that they can be easily handled during application. The lotions were easily redispersible by slight shaking though they underwent sedimentation. Sedimentation volume values indicate that freeze dried aloe powder lotion was more stable than conventional lotion. The sensitivity test, psychometric effect test, indicates that lotions were compatible with the skin.

The in vitro SPF value for freeze dried aloe powder lotion was found to be more than conventional lotion(Table 2). For freeze dried powder lotion, in vitro SPF by Mansur et al method was found to be 13.52±0.21 and the percentage UVB blockage was found to be 46.85% by the spectral transmittance method and the UVA ratio was found to be

Table: 1 The evaluated parameters of various lotions

Evaluation parameter	Calamine lotion	Aloe gel lotion	Freeze dried powder lotion	Novel lotion
I) Physical evaluation
a) P^H	10.05	9.8	8.9	7.24
b) Colour	pink	pink	pink	pink
II) Rheological study
a) Viscosity(cps)	900	1070	1150	1260
b) spreadability(gm.cm/sec)	12.5	13.3	16.6	-------
III)Stability
a). sedimentation volume	0.67	0.7	0.77	0.81
b) redispersibility	Redispersible	Redispersible	Redispersible	Redispersible
c) Freeze thaw cycle	Forms aggregate	Forms aggregate	Forms aggregate	Forms aggregate
d) creaming	Separation of phases	Separation of phases	Separation of phases	Separation of phases
IV) Effectiveness
a) SPF in vivo	2.84±0.72	3.07±0.58	10.03±1.017	12.23±0.36
b) SPF in vitro	------	6.39±0.1	13.52±0.21	------
c) sensitivity	No irritation	No irritation	No irritation	No irritation
d) Psychometric effect	No change was observed	No change was observed	No change was observed	No change was observed

Table 2: In -vitro determination of SPF values of aloe vera conventional and freeze dried powder lotions:

S. No	Wave length	EE value	Mean abs of freeze dried lotion(2mg/ml)	% Transmission of aloe gel lotion	Mean abs of aloe gel lotion(2mg/ml)	% Transmission of freeze dried lotion
1	290	.0150	0.354±0.05	44.6	0.162	68.8
2	295	.0817	0.326±0.07	47.1	0.150	70.7
3	300	.2874	0.298±0.12	50.7	0.137	72.9
4	305	.3278	0.273±0.04	53.6	0.125	74.9
5	310	.1864	0.238±0.08	57.2	0.115	76.7
6	315	.0839	0.226±0.05	59.3	0.097	79.9
7	320	.018	0.224±0.07	59.6	0.084	82.4
8	325	-----	0.212±0.09	61.3	0.072	86.8
9	330	-----	0.204±0.15	61.5	0.066	87.5
10	335	-----	0.201±0.11	62.9	0.062	88.1
11	340	-----	0.190±0.06	64.4	0.056	88.9
13	345	-----	0.181±0.05	65.7	0.050	89.1
14	350	-----	0.167±0.06	67.9	0.046	89.7
15	355	-----	0.165±0.11	68.2	0.040	90.2
16	360	-----	0.158±0.09	69.4	0.036	91.9
17	365	-----	0.155±0.12	69.9	0.035	92.1
18	370	-----	0.149±0.05	70.8	0.030	93.1
19	375	-----	0.146±0.07	71.3	0.028	93.5
20	380	-----	0.140±0.11	72.4	0.026	93.9
21	385	-----	0.135±0.08	73.1	0.024	94.2
22	390	-----	0.130±0.13	74.1	0.022	94.9
23	395	-----	0.122±0.08	75.4	0.022	94.9
24	400	-----	0.109±O.07	77.6	0.021	95.1

Table 3: In vitro testing parameters for conventional and Freeze dried powder lotions

S. No	Parameter	Freeze dried powder lotion	*Aloevera* conventional lotion
1	In-vitro SPF	13.52±0.21	6.39±0.1
2	UVA and UVB blocking capacity	46.85 and 34.26	13.94 and 24.9
3	UVA ratio	1.322	0.729
4	Critical wavelength	385	370

Table4: The evaluated parameters of the microcapsules

S. No	Evaluation parameter	Result
1	Shape	Spherical
2	Diameter	0.510±0.143mm
3	Crushing strength	Powder exudes out

TABLE 5: In vivo determination of SPF values of freeze dried lotions:

S.No	Time to produce erythema on intact skin(min)	Time to produce erythema for calamine lotion(min)	Time to produce erythema for freeze dried lotion(min)	Time to produce erythema for freeze dried powder alone (min)	SPF
1	10	30	132.1	102.1	10.21
2	12	33	150.6	117.6	9.82
3	15	40	166.9	126.9	8.46
4	8	25	114.8	89.8	11.23
5	11	30	144.4	114.4	10.42

TABLE 6: In vivo determination of SPF values of conventional lotions:

S.No	Time to produce erythema on intact skin(min)	Time to produce erythema for calamine lotion(min)	Time to produce erythema for aloe gel lotion(min)	Time to produce erythema for aloe gel alone(min)	SPF
1	10	30	64.5	34.5	3.45
2	12	33	67.5	34.5	2.88
3	15	40	76.6	36.6	2.44
4	8	25	56.3	31.3	3.91
5	11	30	59.7	29.7	2.73

1.322( If UVA ratio >0.8, it is considered as a good UVA blocker), as determined by Boot star system and the critical wavelength was found to be 385( If c>370, it is considered as a broad range sun screen protectant) from critical wavelength method for conventional lotion, SPF by Mansur et al method was found to be 6.39±0.1. the percentage UVB blockage was found to be 24.9 by the spectral transmittance method. UVA ratio was found to be 0.970 (If >0.8, it is considered to be a good UVA blocker). By critical wavelength method the critical wavelength was found to be 375 ( If >370, it is considered as a broad range sun screen protectant). By observing and comparing the above data(Table 3), it can be concluded that the freeze dried powder lotion provides greater sunscreen protection than the conventional lotion.

Correlation between the SPF value measured by the in vitro method and the in vivo method was shown in the fig.1and 2. The absorption of the sunscreen ingredient by the skin may be a determinant factor for the SPF value for the in vivo method. The difference in skin prototype probably lead to this bias. Subjects with skin prototypes I, II and III were suggested for in vivo testing by the US, European countries and Japan, while subjects with skin type II, III, and IV were recruited in this study. The minimum erythemal dose (MED) for unprotected skin of types II, III and IV were expected to be larger than those for types I. As a result the time taken for the erythemal appearance on the skin of the type II, III,IV prototypes was found to be more.

Another strategy we tried to promote stability is to produce bead form of freeze dried Aloe vera leaf gel powder using ionic gelation technique. The formation of beads of freeze dried aloe vera leaf gel powder using calcium alginate was a simple and rapid process. Beads formed were in spherical shape and having diameter 0.510mm±0.143. When beads were pressed over butter paper freeze dried aloe vera leaf gel powder exudes out easily showing easy to squeezing of gel from bead at the time of application(Table 4). The prepared novel lotion was also evaluated for physical and rheological parameters. The p^Hof the novel lotion was found to be 7.24 which indicate that it is more compatible with the skin compared with other lotions. Sedimentation volume values indicate that novel lotion was most stable of all lotions. The sensitivity test, psychometric effect test, indicates that novel lotion was compatible with the skin. The in vivo SPF value of novel lotion (Table 5) was found to be higher than other prepared lotions(Table 6). The polymer concealed the core material from the external environment and as a result, its potency was retained and also the ability of polymers to reflect the UV radiation aids in it.

CONCLUSION:

The present work concluded that herbal extract can be incorporated into lotions with compatibility. Freeze dried Aloe vera leaf gel powder can be incorporated in lotions to improve the protection of skin for long duration from UV exposure. The ionic gelation technique can be used successfully for promoting the stability of freeze dried Aloe vera leaf gel powder.

REFERENCES:

1. Principles of anatomy and physiology by Gerard J. Tortora and Bryan Derrickson, 11^thedition, 2006; chapter 5, 145-162.

2. Mukhtar H, Elmets C. A. Photocarcinogenisis: mechanisms, models and human health implications. Photochem protobiol 1996; 63, 355-447.

3. Stege H, Budde, Grether-beck, Richard, Rougier, Ruzicka, Krutmann. Sunscreens with high SPF values are not equivalent in protection from UVA induced polymorphous light eruption. European journal of dermatology 2002; 12(4): 4-6.

4. Forever Good Health, The Aloe Way, health care magazine, Forever Living Products; India, Pvt. Ltd, 2009; 3-22.

5. Indian Pharmacopoeia 1996, Ministry of Health nd Family Welfare, The controller of publications, New Delhi, Volume-1, 1996:123.

6. Ashawat M S, Saraf S, Swarnalata Saraf. Comparative sun protection factor determination of fresh aloe vera gel vs marketed formulation. Indian J Pharm. Educ. Res 2008; 42(4): 319-322.

7. Shika Srivastava, Shweta kapoor, Swarnalata Saraf. Novel preparation and evaluation of lotion containing aloe gel beads. Indian J Pharm. Educ. Res 2008; 42(2): 170-173.

8. Sankar V, Chandrasekaran A K, Durga S. Formulation and stability evaluation of diclofenac sodium ophthalmic gels. Indian J. of Pharm. Sci 2005;67(4): 473-476.

9. Sakarkar D M, Shrikhande V N. Studies on formulation development, characterization and transdermal permeation of nimesulide from emulgel. Int. J. Pharma. Excip 2004;3(3):57-61.

10. Patrick j. sinko, physical, chemical and biopharmaceutical principles in the pharmaceutical sciences, martins physical pharmacy and pharmaceutical sciences, 2005; 5^thedition:502.

11. Leon Lachman, Herbert A. Lieberman, Joseph L. Kanig, The Theory and practice of Industrial Pharmacy, 3^rd edition, Varghese publication House, Bombay,1987,493.

12. Sreenivasa reddy M, Mutalik S.Preparation and evaluation of minoxidil gels for topical application in alopecia. Indian J. Of Pharm. Sci. 2006; 68(4):432-436.

13. Spruce, S.R; J.P. Hewitt, In vitro SPF methodology and correlation with In vivo data. Euro cosmetics. June 1995;14-20.

14. Freitas Z M F, Goncalves J C S, Santos E P and Vergnainin A. Glyceridic Esters Of P- Methoxy cinnamic acid. A new Sun screen of the cinnamate class. Int. J. Cosmetic sciences 2001;23,147.

Received on 28.12.2010 Accepted on 05.05.2011

Res. J. Topical and Cosmetic Sci. 2(2): July – Dec. 2011 page 66-70