Photoprotective potential of Saharan myrtle (Myrtus nivellei) Leaves

 

Amira Mansour1*, Ghania Rahili2, Chawki Bensouici3

1Centre De Recherche Scientifique et Technique En Analyses Physico-Chimiques (CRAPC),

BP 384-Bou-Ismail, Tipaza, Algeria.

2Institut National De La Recherche Forestičre (INRF), Baďnem - BP 37, Cheraga, Algiers, Algeria.

3Centre De Recherche En Biotechnologie, Ali Mendjli, Nouvelle Ville UV 03, BP E73, Constantine, Algeria.

*Corresponding Author E-mail: mansour.amira13@yahoo.com

 

ABSTRACT:

In-vitro sunscreen activity of cream formulation containing the different extracts of M. nivellei leaves was evaluated through sun protection factor (SPF) determination, by absorption spectroscopy method. All formulations displayed high potency in photoprotection (SPF>40) at 10000 ppm when compared to the cream without extract (SPF=7). Furthermore, the free radical scavenging activity of the different extracts was measured by the DPPH assay. Ethyl acetate extract exhibited the highest potency in scavenging free radicals comparable to BHA. The photoprotective and antioxidant properties of leaves extracts of M. nivellei indicate that this plant is a promising candidate for use in cosmetic formulations.

 

KEYWORDS: Myrtus nivellei; Saharan myrtle; Sunscreen activity; Sun protection factor; Antioxidant activity.

 

 


INTRODUCTION:

Long exposure to ultraviolet (UV) radiations reaching the earth from the sun is known to cause several damaging effects to the skin, such as erythema, hyperpigmentation, photoaging, and skin cancer1,2,3. The most popular way to protect skin against UV radiation’s harmful effects is topical application of sunscreen products. The efficacy of sunscreen products is first given by the sun protection factor (SPF), which is the quotient between the minimal erythema dose (MED) with applied sunscreen and the MED without sunscreen. Therefore, the SPF is an indicator of protection against UVB radiation (Table 1). 

 

Conventional sunscreen products contain several synthetic chemicals available as photoprotective agents that are or can be harmful for our health. These synthetic molecules have limited concentration according to regulation concern. The main problem of the chemical sunscreen agents are the photoirritation, photosensitization and contact dermatitis4.

 

Table 1: The different levels of protection provided by sunscreen cosmetics.

Category

SPF measured

Labeled SPF

Low Protection

6-14

6-10

Medium Protection

15-29

15-20-25

High Protection

30-59

30-50

Very high Protection

> 60

50+

 

In recent years, it has been observed an increasing interest for use of compounds derived from natural sources with UV absorption property to substitute synthetic sunscreen agents. In addition to UV absorption property, most natural compounds were found to act as antioxidants, anti-inflammatory, and immunomodulatory agents5, which provide further protection against the damaging effects of UV radiation exposure.

Myrtus nivellei Batt. & Trab. (Myrtaceae) the Saharan myrtle6, called Tefeltest in Touareg language, have been used in folk medicine. According to ethnobotanical investigation, in the tassili region of Algeria, the crushed leaves added to oil or butter ointment (poultice) are recommended in the treatment of dermatosis and for hair care7. Previously we reported the high content of phenolic compounds in this plant8. The purpose of the present study was to evaluate the in-vitro sun protection factor (SPF) of cream formulation containing extracts of M. nivellei leaves by ultraviolet (UV) spectroscopy method. The free-radical scavenging activity of all extracts was measured by the DPPH assay.

 

MATERIEL AND METHODS:

Plant material:

Leaves of M. nivellei Batt & Trab were collected in March 2011 at Tamanrasset area, located in Algerian Sahara. The plant was identified by Mrs Boutamine Rabia from the laboratory of ecology INRF (National Institute of Forest Research) of Tamanrasset (Alger). A voucher specimen (MN311) has been deposited in the INRF of Tamanrasset.

 

Extraction:

Air-dried and coarsely powdered (200g) leaves were macerated at room temperature with MeOH–H2O (80:20, v/v) for 24 h, and the operation was repeated three times. After filtration, and concentration in vacuo of the combined solutions, the residue was diluted with distilled water and successively extracted with hexane, dichloromethane, ethyl acetate and n-BuOH, The organic phases were concentrated in vacuo at room temperature to obtain the following extracts: hexane (1.2g), dichloromethane (0.95g), EtOAc (3g) and n-butanol (6.1 g) respectively.

 

Preparation of cream:

Moisturizer cream Glycerin was acquired in a local pharmacy. 10% of each extract (hexane, dichloromethane, ethyl acetate, n-butanol, and methanol) of M. nivellei leaves were incorporated in the glycerin cream base.

 

Determination of in vitro Sun Protection Factor (SPF):

The SPF determination model used in this study was based on the equation proposed by Mansur et all.9. 100 mg of samples (cream) was weighed, diluted with 10mL of ethanol, followed by ultrasonication for 5 min and filtered through cotton, to give 10000ppm solution, then different concentrations (dilutions) were prepared to give 5000, 1000, 500, 250ppm solutions using ethanol. The same method was used to determine the SPF of Glycerin (without extract). The absorption spectra of samples solutions were obtained in the range of 290-320nm every 5 nm in a 96-well plate, using the plate reader Perkin Elmer Multimode EnSpire. Triplicates were made. Following the Mansur equation (eq.1), the obtained absorbance values Abs (λ) were multiplied with the respective EE (λ) x I (λ) values and then summation was taken and multiplied with the correction factor 10.

 

SPFspectrophotometric = CF ×   (eq.1)

Where CF is the correction factor (= 10); EE (λ) is the erythemal effect of radiation; I (λ) is the solar intensity spectrum; Abs (λ) is the absorbance of sunscreen product. The values of EE (λ) x I (λ) are constants determined by Sayre et al.10.

 

DPPH radical-scavenging activity:

The antiradical activity of all extracts were determined using the stable 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) assay11. 160µL of DPPH solution (0.1mM in methanol, prepared daily) was added to 40µL of various concentrations (ranged from 3.12. to 200µg/ml) of each sample in MeOH solution. After 20 min in dark at room temperature, the decrease in absorbance was measured at 517nm against a blank consisting of an equal volume of methanol. BHT and BHA were used as positive controls. The DPPH concentration in the reaction medium was calculated from a calibration curve analyzed by linear regression and IC50 (mean effective scavenging concentration) was the concentration (in micrograms per milliliter) of sample necessary to decrease the initial DPPH concentration by 50%. A lower IC50 value indicates stronger antioxidant activity. All tests were performed in triplicate.

 

RESULTS AND DISCUSSION:

SPF of samples (cream with leaves extracts), and glycerin cream (without leaves extract) was evaluated and calculated through UV Spectrophotometric method. The SPF values are shown in table 2.

 

At 10000ppm, SPF of cream containing 10% of leaves extract was found to be very high >40 for all extracts. At 5000ppm the SPF was found to be 29.17±0.53 and 28.75±0.59 for creams containing methanol and dichloromethane extracts respectively, providing a high level of sun protection, and >39 for creams containing hexane, ethyl acetate, and n-butanol extracts providing a very high level of protection. At 1000ppm SPF was found to be 10.85±0.34, 10.15±0.43 and 14.46±0.7 for creams containing methanol, dichloromethane and n-butanol extracts respectively, and therefor provides a low sun protection, whereas creams containing hexane and ethyl acetate extracts provides a medium level of sun protection with an SPF of 16.82±0.26 and 16.10±0.23 respectively. At 500 and 250ppm, SPF was low for all extracts.

 


Table 2: Determination of Sun protection Factor (SPF) Values for Cream of extracts of Myrtus nivellei leaves.

Conc

(ppm)

SPF ± SD

Methanolic Extract

Hexane Extract

Dichromethaneextract

Ethyl acetateextract

n-butanolextract

Glycerincream

10000

5000

1000

500

250

43.74 ± 0.21

29.17 ± 0.53

10.85 ± 0.34

9.19 ± 0.37

7.8 ± 0.19

45.5 ± 1.09

43.26 ± 075

16.82 ± 0.26

12.33 ± 0.14

9.61 ± 0.37

40.3 ± 0.04

28.75 ± 0.59

10.15 ± 0.43

8.97 ± 0.23

8.03 ± 0.5

43.74 ± 0.5

42.88 ± 0.44

16.10 ± 0.23

12.09 ± 0.4

9.26 ± 0.4

42.96 ± 0.54

39.53 ± 0.89

14.46 ± 0.7

10.33 ± 0.05

8.24 ± 0.12

7.56 ± 0.32

6.74 ± 0.08

6.27 ± 0.3

6.19 ± 0.2

6.2 ± 0.27

 


Thus is appears clearly that the SPF of creams containing hexane and ethyl acetate extracts was the highest comparing with creams containing the other extracts, at all concentrations. These results suggested that the developed cream containing leaves extracts of M. nivellei, especially hexane and ethyl acetate extracts have remarkable potential of sun protection.

 

The free radical scavenging activity of all extracts was evaluated by the DPPH assay, and compared with the values of BHT and BHA. The IC50 values are reported in table 3.

 

Table 3: Antioxidant activity by the DPPH assay of extracts of Myrtus nivellei leaves.

Extract

IC50 (µg/mL)

Methanol

Hexane

Dichloromethane

Ethyl acetate

n-butanol

BHT

BHA

13.36±0.64

87.53±2.55

46.8±2.98

6.98±0.45

8.49±0.14

22.32±1.19

5.73±0.41

 

Methanol, ethyl acetate, and n-butanol extracts displayed a strong concentration-dependent free radical scavenging activity in the DPPH test (IC50 = 13.36, 6.98, 8.49 µg/mL respectively) higher than BHT (IC50 = 22.32 µg/mL) used as positive control, among them ethyl acetate extract exhibited the highest potency in scavenging free radicals comparable to BHA (IC50 = 5.73 µg/mL). Hexane, and dichloromethane extracts showed less potent activity (IC50 = 87.53 and 46.8 µg/mL respectively).

 

By comparing the results of Free radical scavenging activity with the SPF values of each extract, we noted that the extract which has displayed the highest SPF (hexane extract), exhibited the weakest antioxidant activity, suggesting that there is no correlation between SPF and the free-radical scavenging activity of M. nivellei.

 

However, these results have shown the high free-radical scavenging activity and the high sun protection potency of M. nivellei leaves, correlated undoubtedly with its richness on sunscreen compounds.

 

CONCLUSION:

These results suggested that leaves extracts of M. nivellei, seems to be remarkable against skin damages and skin cancer considering their high sunscreen potential in addition to their richness of phenolic compounds recognized by their numerous biological and pharmacological effects12,13, mainly antiinflammatory and antioxidant effects. Furthermore M. nivellei leaves have a big potential to be substitutes for synthetic sunscreen agents in cosmetics and anti-wrinkle skincare.

 

ABBREVIATIONS:

M. nivelei: Myrtus nivelei

SPF: sun protection factor

BHT: butylated hydroxytoluene

BHA: butylated hydroxyanisole

DPPH: 2,2-diphenyl-1-picrylhydrazyl

 

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Received on 07.10.2019            Accepted on 31.12.2019           

Accepted on 21.01.2020              ©A&V Publications all right reserved

Research J. Topical and Cosmetic Sci. 2020; 11(1):12-14.

DOI: 10.5958/2321-5844.2020.00003.5