Superantioxidant Kakadu Plum: antimicrobial and anti-inflammatory activities.
Terminalia ferdinandiana is an Australian native flowering plant which only grows throughout the tropical woodlands in north Australia (Figure 1). The fruit, generally known as Kakadu plum, has been traditionally used in Australian aboriginal community as an antiseptic, soothing balm, and in the treatment of cold, flu and headache .
Figure 1. The distribution of Kakadu plum plant in Australia and the look of the fruit. (Source: https://avh.ala.org.au)
Antioxidants in Kakadu plum
Kakadu plum is an antioxidant-rich fruit. It has a high concentration of vitamin C, ranking among the highest known of any natural source . Besides, Kakadu plum also contains a high level of many other antioxidants including vitamin E, phenolic compounds and flavonoids. Table 1 below summarised the major antioxidants contained in Kakadu plum and its strong antioxidant capacity.
Table 1. Antioxidant activity of Kakadu plum.
|Vitamin C||2300–3150 mg/100g ||Kiwi: 92.7mg/100g Orange: 50mg/100g|
|Vitamin E||1.0 mg/100g ||1.5-fold higher than blueberry|
|Total phenolic compounds||307.6 mg/100g ||6-fold higher than blueberry |
|Oxygen radical-scavenging capacity||4.1-fold of blueberry |
|Total reducing capacity||13.1- fold of blueberry |
In addition to rich antioxidants, Kakadu plum is also a good source of the minerals including magnesium, zinc, calcium, potassium, sodium, iron, phosphorous, manganese, copper, and molybdenum .
Antimicrobial activity of Kakadu plum extract
A recent study demonstrated the antimicrobial activity of extracts from the fruit and leaves of Kakadu plum, which showed strong inhibition against the foodborne bacteria Methicillin resistant Staphylococcus aureus, and clinical isolates of Pseudomonas aeruginosa .
As shown in Figure 2, the images captured by scanning electron microscopy (SEM) images of the treated bacteria showed that the presence of Kakadu plum extract leads to the morphological changes and cell death. These results suggest that antioxidant rich extracts of Kakadu plum have potential applications as natural antimicrobials in food preservation.
Figure 2. Scanning electron microscopy (SEM) images of methicillin resistant Staphylococcus aureus (A) affected by Kakadu plum fruit extracts (B) and leaf extracts (C), and clinical isolates of Pseudomonas aeruginosa (D) affected by fruit extracts (E) and leaf extracts (F) .
Antiinflammatory activity of Kakadu plum
Autoimmune inflammatory diseases, such as rheumatoid arthritis and multiple sclerosis, can be triggered by specific bacteria in susceptible individuals. Since Kakadu plum has exhibited therapeutic properties as an antimicrobial agent, it has also been shown to inhibit several microbial triggers of autoimmune inflammatory diseases.
Researchers from Griffith University in Australia have implemented systematic studies to demonstrate that the stilbene and tannin components in Kakadu plum displayed good inhibition against the bacteria strains rheumatoid arthritis , while the phytochemicals inhibited bioactivity against the bacterial triggers of multiple sclerosis . The studies concluded all Kakadu plum extracts were nontoxic in the bioassay and indicated their potential as medicinal agents in the treatment and prevention of autoimmune inflammatory diseases.
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