Physical properties of aloe vera
Aloe vera is a cactus-like plant which has a stem with triangular, fleshy leaves ranging in colour from grey-green to bright green (Fig 1 A and B) and in the margin of the leaves has small white teeth. The leaves were composed of three layers: an inner gel, a yellow sap and the outer thick layer (Fig 1C).
Fig 1: Aloe vera (Aloe barbadensis miller). A. Aloe vera plant. B. Aloe vera leave. C. Cross section of Aloe vera leaves.
The Physical characteristics of fresh Aloe vera leaf i.e. mean values of leaf length, width, thickness, apparent volume, leaf weight, gel weight and gel recovery are depicted in Table 1.
Table 1: Physical parameters of fresh Aloe vera leaf.
It has been observed that the length of the leaf is about 23-25 times its thickness. A similar result was given by Sabat et al., (2018). Sabat et al., (2018)
reported that the physical properties of fresh Aloe vera leaves were correlated with gel yield and it was found that the leaf weight has a direct effect on the gel yield whereas the effect of leaf volume is found to be minimal.
During analysis, it was also observed that leaf weight, apparent volume and gel yield had some relationship. Hence, the apparent volume could be taken as a parameter for the estimation of fresh weight and gel yield and vice versa. The relationship between apparent volume-fresh weight, leaf weight-gel yield and apparent volume-gel yield of aloe leaves is shown in Fig 2, 3 and 4, respectively. The relationship between the apparent volume and fresh weight of Aloe vera leaf is depicted in Fig 2. The relationship between the weights of aloe vera leaves and gel recovery of Aloe vera leaf is depicted in Fig 3. Fig 4 shows the relationship between apparent leaf volume and gel recovery of Aloe vera leaf.
Fig 2: Relationship between apparent volume and fresh weight of Aloe vera leaf.
Fig 3: Relationship between weights of Aloe vera leaves and gel recovery of Aloe vera leaf.
Nutrient composition of Aloe vera leaf
Fig 4: Relationship between apparent leaf volume and gel recovery of Aloe vera leaf.
The proximate analysis (on a dry matter basis) revealed that the leaf pulp of Aloe vera contained 91.12% of moisture, 8.75% of crude protein, 2.4% of ether extract, 16.8% of crude fibre, 52.0% of carbohydrate, 12.5% of total ash and 238kcal of energy.
Mineral estimation of leaf pulp of Aloe vera revealed the highest presence of magnesium (8310.0 ppm) followed by calcium (2532.0 ppm), phosphorus(870.1 ppm), zinc (41.8 ppm), selenium (40.1 ppm), chromium (4.5 ppm) and copper (0.57 ppm).
Amany et al. (2020)
reported that the leaf pulp of Aloe vera contained 98.5 to 99.5% of water. Gautam and Awasthi (2007)
analyzed the nutrient composition and physico-chemical characteristics of Aloe vera (Aloe barbadensis
) powder at Pantnagar, India and they stated that it contained 18.5% crude fiber, 4.8% crude protein, 2.2% crude fat, 14.0% total ash, 48.0% carbohydrate and 231 kcal energy value. They also stated that Aloe vera contained substantial amounts of iron (64.8 mg/100 g), ascorbic acid (27.0mg/100 g) and β-carotene (335.8 mg/100 g). Dietary fiber was 21.3% while reducing and non-reducing sugars each were 76 mg/10 g. Results of chemical analysis in Faisalabad, Pakistan using whole leaves (on a dry matter basis) also showed that it contains 6.86–15.4% of crude protein, 60.34-72.17% of crude fibre and 14.65-16.88% of ash (Ahmed and Hussain, 2013
; Khan et al., 2014)
which was higher than the present study, might be due to geographical variation as well as soil pattern of the Mizoram.
Analysis of mineral elements is most important to understand the pharmacological and nutritional values of medicinal plants. In the present study, it was found that magnesium, calcium, phosphorus, zinc and selenium were abundantly present in Aloe vera leaves which are essential for metabolism, reproduction, immunological system and growth of connective tissues in the animal (Pawar and Kamble, 2015)
. Amany et al., (2020)
stated that the dietary supplementation of Aloe vera (0.1-1.0%) positively increased body weight of poultry by 7-25% and improved immunological indices by 10-50%. They also stated that the feed treatment with 0.5-1% Aloe vera reduced harmful bacteria in the gut by 24% and increased beneficial bacterial populations by 30%. Due to its functional and therapeutic properties, the use of Aloe vera as a feed ingredient in livestock and poultry rations has increased. Finally, regardless of the technical inconsistencies and differences, levels and types of constituents vary according to geographic location, variety or origin, for that reason, the identification of their active constituents is essential for the best use of the plant (Choi and Chung, 2003)
Phytochemical screening of Aloe vera gel
The results for the phytochemical screening of Aloe vera gel extract using a different solvent in different polarity were represented in Table 2.
Table 2: Phytochemical composition of Aloe vera.
Aqueous and ethanol extraction methods revealed the presence of steroids, alkaloids, glycosides, carbohydrates, tannins and tarpenoid in Aloe vera. TLC analysis showed five spots Rf (0.10, 0.30, 0.40, 0.60, 0.78) in Toluene: Ethyl acetate: Methanol: Acetic acid (7:3:1:02) solvent system (Fig 5).
Fig 5: Visualisation of TLC separation of extract of Aloe barbadensis miller under white light.
An ascending chromatography gives an idea about the possible compounds that can be present in the extract from the number of spots. The presence of tannins, saponins, alkaloids, flavonoids and glycosides in Aloe vera was also reported by Mohammed et al., (2020). Darshan (2017)
reported that Aloe vera contains saponin, alkaloids and flavonoids in methanol extraction. These types of phytochemicals are involved in plant defence mechanisms against various microorganisms with steroids involved in antibacterial properties, flavonoids with anti-oxidant function and tannins are known to be involved in the anti-cancer action (Jannathul et al., 2019).
All the phenolic compounds are involved in scavenging free radicals with their reducing properties. All these compounds are of pharmaceutical importance as they possess properties such as anti-cancer, anti-diabetic, analgesic, antibacterial and antifungal activity (Jannathul et al., 2019).