During the course of the fruit extraction, I've been experimenting with two extraction types lately, one being water extraction and the other being ethanol 95%. When tested with the same five microbes, these are the results:
1) Water extraction
From these tests I can conclude that both extract had somewhat of an inhibition activity towards microbes tested. A clear ring is seen around the disks for both extract types (except conc 25% and below). However, water extraction is not very effective in showing anti m/o activity. There is a huge difference in the two activities, even of similar fruits with similar maturity. According to the S/V, since ciku is full of polyphenols and other antioxidants (non-polar solvent soluble), those activities may be more observable in non-polar solvent.
One other reason that proved this is the fact that Ciku has very high antioxidant capacity. L-ascorbic acid equivalent antioxidant capacity, AEAC, is the highest compared to other local fruits such as starfruit, guava, salak, pineapple and so on.
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| from Leong and Shui, 2001 |
In this experiment above, the ciku used is unripe. Fruit is peeled and blended, and mixed into 50% ethanol at 1:10 w/v, and centrifuged to obtain supernatant. This is different than the method I encountered which used ripe fruits (H. N. Sin et al, 2006) . However, after many unsuccessful attempts with ethanol extract (very little antimicrobial activity), I may conclude that ethanol may not be fully optimized for these kind of fruits. I may need other types of extracting solvent. A few suggestions are hexane, acetone and methanol.
One research delved on the various types of extraction, and chose acetone as the preferred solvent (Shui, Wong, and Leong, 2004). Acetone 50% is used directly to extract pulp of ciku for 45 minutes at 90C. Then it is rapidly cooled to room temperature before centrifugation at 14000g. This extract is used for spectrophotometry testing of TPC. Another research (Chong et al, 2005) also uses acetone (70%), but after it the ciku was homogenized it in ultrasonic bath for 30 minutes before centrifuging it for 15 min at 5000rpm. This is different than Ma et al, (2003), who uses methanol for ciku extraction and later fractionate it using hexane and ehtyl acetate.
Another possible error (while doing ethanol extraction) is the drying part. Previously I used "room temperature drying", i.e. 26-28C, to dry the ciku before extraction as specified by Jayakumar and Kanthimathi (2011). However, it is recently found out by Chong et al (2009), that the higher the drying temperature the higher the phenolics in the ciku.
One research delved on the various types of extraction, and chose acetone as the preferred solvent (Shui, Wong, and Leong, 2004). Acetone 50% is used directly to extract pulp of ciku for 45 minutes at 90C. Then it is rapidly cooled to room temperature before centrifugation at 14000g. This extract is used for spectrophotometry testing of TPC. Another research (Chong et al, 2005) also uses acetone (70%), but after it the ciku was homogenized it in ultrasonic bath for 30 minutes before centrifuging it for 15 min at 5000rpm. This is different than Ma et al, (2003), who uses methanol for ciku extraction and later fractionate it using hexane and ehtyl acetate.
Another possible error (while doing ethanol extraction) is the drying part. Previously I used "room temperature drying", i.e. 26-28C, to dry the ciku before extraction as specified by Jayakumar and Kanthimathi (2011). However, it is recently found out by Chong et al (2009), that the higher the drying temperature the higher the phenolics in the ciku.
