343
(pyridoxal phosphate) and vitamin B 12 (cyanocobalamin) along with presence of
various inorganic minerals (copper, calcium, phosphorus, magnesium, potassium,
zinc, iron, copper, manganese, molybdenum and sodium). According to researches,
the diverse biological activities of different Aloe species is due to synergistic action
between numerous compounds instead of single chemical compound. The various
phytoconstituents present in different parts of Aloe species are presented in Table 18.2.
Many beneficial activities of the plant have been reported and attributed especially to the plant’s polysaccharides. The activities may include, anti-bacterial, antiviral, anti-inflammatory property, laxative, immunomodulation, and protection
against radiations.
The various polysaccharides isolated from the plant include galactan, mannan,
arabinanarabinorhamnogalactan, glucuronic acid-containing polysaccharide, and
pectic substance. Mannan and pectic substance have been found to be the primary
polysaccharides with some studies suggesting mannan to be the main polysaccharide while still others suggesting pectic substance to be the main one (Ovodova et al.
1975; Mandal and Das 1980). These controversies have been attributed to the plant’s
different geographical occurrences (Mandal and Das 1980; Grindlay and
Reynolds 1986).
The leaves of the Aloe vera plant have shown strong antioxidant activities. One
study showed that the plant is more antioxidant than some of the standards like butylated hydroxytoluene (BHT) and α-tocopherol. The study was conducted using plants
of different age such as 2–4 year old plants. It was determined that the 3 years old
plant contained a significantly higher number of flavonoids and polysaccharides than
the 2 and 4 years old plants. Also the extract of the 3 year old plant showed a higher
antioxidant potential than the extracts of 2 years old plants in the first 10 min of the
experiment. When the different plant’s extracts were ranked in terms of their antioxidant activity along with butylated hydroxytoluene (BHT) and α-tocopherol, it was
found that in first 10 min α-tocopherol had the highest antioxidant potential while the
3 years old plant was at the second highest rank. However when their antioxidant
potential was observed for 110 min it was observed that radical scavenging potential
of α-tocopherol had decreased significantly ranking the 3 years old plant’s extract at
the highest point in terms of showing antioxidant potential. The study also concluded
that the 2 years old plant showed the lowest antioxidant activity (Hu et al. 2003).
The plant contains very high amounts of the phenolic compounds such as
anthrones, anthraquinones, chromones, saponins, coumarins, and polysaccharides
in the leaf gel. The phenolic compounds have been attributed to showing antioxidant
activities of the plant (Rice-Evans et al. 1997).
18.3.1 Anthraquinones
Several anthraquinones occur in roots and leaves of the species of aloe genus. Aloe
emodin is found widely in the species of aloe and is found mostly in leaves of the
plant. The roots of aloe contain two types of anthraquinones such as aloe saponarin
18 Aloe Species as Valuable Sources of Functional Bioactives
(pyridoxal phosphate) and vitamin B 12 (cyanocobalamin) along with presence of
various inorganic minerals (copper, calcium, phosphorus, magnesium, potassium,
zinc, iron, copper, manganese, molybdenum and sodium). According to researches,
the diverse biological activities of different Aloe species is due to synergistic action
between numerous compounds instead of single chemical compound. The various
phytoconstituents present in different parts of Aloe species are presented in Table 18.2.
Many beneficial activities of the plant have been reported and attributed especially to the plant’s polysaccharides. The activities may include, anti-bacterial, antiviral, anti-inflammatory property, laxative, immunomodulation, and protection
against radiations.
The various polysaccharides isolated from the plant include galactan, mannan,
arabinanarabinorhamnogalactan, glucuronic acid-containing polysaccharide, and
pectic substance. Mannan and pectic substance have been found to be the primary
polysaccharides with some studies suggesting mannan to be the main polysaccharide while still others suggesting pectic substance to be the main one (Ovodova et al.
1975; Mandal and Das 1980). These controversies have been attributed to the plant’s
different geographical occurrences (Mandal and Das 1980; Grindlay and
Reynolds 1986).
The leaves of the Aloe vera plant have shown strong antioxidant activities. One
study showed that the plant is more antioxidant than some of the standards like butylated hydroxytoluene (BHT) and α-tocopherol. The study was conducted using plants
of different age such as 2–4 year old plants. It was determined that the 3 years old
plant contained a significantly higher number of flavonoids and polysaccharides than
the 2 and 4 years old plants. Also the extract of the 3 year old plant showed a higher
antioxidant potential than the extracts of 2 years old plants in the first 10 min of the
experiment. When the different plant’s extracts were ranked in terms of their antioxidant activity along with butylated hydroxytoluene (BHT) and α-tocopherol, it was
found that in first 10 min α-tocopherol had the highest antioxidant potential while the
3 years old plant was at the second highest rank. However when their antioxidant
potential was observed for 110 min it was observed that radical scavenging potential
of α-tocopherol had decreased significantly ranking the 3 years old plant’s extract at
the highest point in terms of showing antioxidant potential. The study also concluded
that the 2 years old plant showed the lowest antioxidant activity (Hu et al. 2003).
The plant contains very high amounts of the phenolic compounds such as
anthrones, anthraquinones, chromones, saponins, coumarins, and polysaccharides
in the leaf gel. The phenolic compounds have been attributed to showing antioxidant
activities of the plant (Rice-Evans et al. 1997).
18.3.1 Anthraquinones
Several anthraquinones occur in roots and leaves of the species of aloe genus. Aloe
emodin is found widely in the species of aloe and is found mostly in leaves of the
plant. The roots of aloe contain two types of anthraquinones such as aloe saponarin
18 Aloe Species as Valuable Sources of Functional Bioactives