Wednesday, January 18, 2017

English corner - (Aflatoxins and Ochratoxins)

Aflatoxins, as well as ochratoxin generally are some of the groups of mycotoxins. Mycotoxins can be describes as toxic microorganisms that can be directly taken by human or animals via food, which can cause danger towards humans’ as well as animals’ health (Basappa, 2009). This has clearly showed that both aflatoxin and mycotoxins has been among some compounds, or microorganisms that contain toxic, as well as carcinogenic properties towards humans’ and animals body system. These toxic compounds can be found in some of the food taken by humans and also animals, and eventually can be ingested thoroughly by them. As a result of this ingestion of toxic compunds, this can give some effects on humans’ and animals’ body systems as those compounds can harm the cell, organs and so on. As a result, the health of infected organisms will be in great danger if those mycotoxin-containing foods are taken by them, especially in very huge quantity. However, if those kinds of foods have only be taken in small amount, this might not give any significant effects towards humans’ and animals’ health.
            Aflatoxins generally were “mycotoxins that are produced by various Aspergillus species including A. flavus, A.parasiticus and A.nominus.” (Chen, Grenier & Applegate, 2013). Other than that, Basappa (2009) has defined aflatoxins as a set of secondary metabolite compounds which has very high toxic as well as carcinogenic properties, produces by some species such as Aspergillus flavus and A.parasiticus. This has meant that aflatoxins are the products of secondary metabolites that mainly forms from aspergillius species of plant, which shows that aflatoxins are originated from plant species. Furthermore, those aflatoxins that formed has their main characteristics in which those compounds are very toxic and has carcinogenic properties, thus these aflatoxins might cause cancer towards infected organisms. Hence, these aflatoxins can be describes as “danger” if taken by organisms, mainly in excessive manner. The examples of plants that contained aflatoxins are maize, some beans and so on.
            Meanwhile, ochratoxins, which also parts of mycotoxins, can be describes as “mycotoxin found as a contaminant in different food matrices such as cereals, beans, dried fruits and beverages such as beer, wine and coffee. This mycotoxin is a secondary metabolite produced by several mould species of Aspergillus and Penicillium” (Vanesa & Ana, 2012). Basically, like the aflatoxins, ochratoxins can also be found as ingredients in some kind of food as mentioned before, which are, for example, cereals, dried fruits, and beans. In addition, those ochratoxins can also been found in some kind of beverages especially in beers, wines and some kinds of coffees. Likewise of those aflatoxins compound, ochratoxins also may harm humans’ as well as animals’ health if those ochratoxin-containing foods and beverages have been taken excessively. This is because, as ochratoxins that are also parts of mycotoxins, these compounds are believed to give toxic and some carcinogenic properties towards the humans or animals that consume food or beverages containing these compounds.
            In this topic “Aflatoxins and Ochratoxins”, first of all, this topic will begin with discussion about the general information about both aflatoxins and ochratoxins. This general information will overview some characteristics of aflatoxins and ochratoxins. This will include the structure, the properties (physical, chemical, toxicology), how to distinguish both compounds and many more. Then, the classifications of aflatoxins and ochratoxins will be discussed in detail, as there are a lot of classifications regarding both types of compounds, for example, Aflatoxin B1, Ochratoxin A and many more. Subsequently, general ideas on both aflatoxins and ochratoxins synthesis will be discussed. Lastly, some examples of health risks/problems that has been caused by both aflatoxins and ochratoxins wil be discussed. For example, effect of aflatoxins on maize production, ochratoxins in coffee and their health risks on human, effects of aflatoxins on poultry production and many more.
             Aflatoxins, as mentioned earlier, are secomdary metabolites produced by some plant species namely Aspergillius flavus and A. parasiticus. Those metabolites formed generally contained high toxic and carcinogenic properties towards humans and animals. Furthermore, as these aflatoxins has been studied to give some teratogenic and mutagenic effects in some experimental animals” (Basappa, 2009), these has shown further effects that can be happened towards animals and humans regarding aflatoxins, such as some cancer, birth defects, mutations and many more. Generally, those toxins that have been contained in the aflatoxins can be simply detected using UV spectrophotometry analysis, and those differences of toxin compounds that has been found in aflatoxins gave the different classifications of aflatoxins such as aflatoxin B1, aflatoxin B2, aflatoxin G1, aflatoxin G2 and so on.
           From the general structure, it can be studied that the difuranucoumarin is the main, or in the other word, the backbone structure of the aflatoxins. Meanwhile, the final part of the general aflatoxin compound is the part that gives different classifications of the aflatoxins. In fact, those parts that show aflatoxins classifications is the part whereby the toxic properties are often found.
           For the properties of aflatoxins, generally, for toxicology properties, those aflatoxins have toxins structure that can give harmful properties such as carcinogenic, mutagenic, teratogenic and many more. However, according to Basappa (2009) and Morteza Azizollahi Aliabadi, Fatemeh (Elham) Alikhani, Mahya Mohammadi and Reza Kazemi Darsanaki (2013), there are some of the classifications of those aflatoxins which are non-toxic, and this non-toxic aflatoxins can be used as treatment and biological control of those aflatoxin-caused health effects.
For chemical properties of aflatoxins, generally, aflatoxins are highly oxygenated compounds. This is due to the large amount of oxygen compounds in the aflatoxin structures. This oxygen in aflatoxins are highly reactive and can undergo redox reaction very easily with humans’ or animals’ body systems if taken, which can cause effect on the chemical compositions in humans’ or animals’ body systems, hence, cause harm towards their health. Furthermore, aflatoxins are heterocyclic compounds, led by coumarin nucleus and surrounded by bifuran, as well as pentanone/lactone structure. All those structures have given significant towards biological functions of aflatoxins as well as their toxicology functions.
            Meanwhile, for ochratoxins, as differed from those aflatoxins which are secondary metabolites, instead, are contaminants that formed in food, for example, cereals, beans, dried fruits, and also in beverages such as beer, wine and coffee. This has meant that as differed from aflatoxins which are secondary metabolites that readily produced by some of the plant species, these ochratoxins are contaminants that has been resulted to be formed by some food and beverages. In short, ochratoxins has only been formed of the food or beverages that have been contaminated by environmental factors.
            Generally, the structure of ochratoxins is based of para-chlorophenol methyl dihydroisocoumarin as parent compound. Then, there were derivatives of amide link of L-phenylalanine at ortho position of the para-chlorophenol parent structure. That structure is generally derived from combinations of coumarin group with para-chorophenol as well as the amide linkage of L-phenylalanine directly to the para-chlorophenolic group. This ochratoxin structure is generally derived from shikimic acid pathway between phenylalanine and malonyl-CoA synthesis of coumarin structure, as well as formation of para-chlorophenolic group and amide linkage to the phenylalanine group. These ochratoxins formed are not the main product of the shikimate pathway phenylalanine and malonyl-CoA synthesis of coumarin derivative structures, however, has been produced as contaminants of both phenylalanine and coumarin reaction schemes.
            For the toxicology properties of this ochratoxin groups, the most notable toxic properties has come from the classification of ochratoxin A. This ochratoxin group has been found mainly in beverages such as beers and mainly in comtaminated coffee samples. Those ochratoxins, which are known as most toxic among ochratoxin groups, has been generally can cause highly damage towards human health. This is because, this ochratoxin A contain dangerous toxicity such as neurotoxins as well as hepatotoxins which can highly affected the neurotransmitter and digestive organs such as liver, gallbladder, pancrease and many more. This can cause huge damage towards human health as neurotransmitter system and digestive system are among the most important human body systems. Therefore, it is very important to ensure that ochratoxins contaminated in the coffee/any beverage samples needed to be isolated and cleaned until the safe level of  “5 mg/kg for roasted coffee beans and ground roasted coffee, and 10 mg/kg for soluble coffee” (Vanesa,& Ana, 2012) has been achieved.
            For physical properties of ochratoxins, generally, these ochratoxins are mainly polar; therefore these ochratoxins can be easily absorbed in our body systems throughout water. Furthermore, the ochratoxins are very permeable towards organ membrane, resulting to easy diffusion towards targeted body systems, or body organs. Next, for chemical properties of the ochtaroxins, as there are a lot of functional groups existed on the structure, this has shown that thess ochratoxins are highly reactive, and a lot of chemical reaction can be derived from this compound. This is the factor that is believed to give toxicological properties towards this ochratoxin compound.
            To proceed, there are several differences between aflatoxins and ochratoxins. Firstly, aflatoxins are the secondary metabolite products that are derived from difuranucoumarins, while ochratoxins are contaminants of phenylalanine’ and coumarin’s shikimic acid reaction schemes. Then, the aflatoxins has given toxicological properties of mainly carcinogenic, mutagenic and teratogenic properties, while ochratoxins give more vastly toxicological properties such as neurotoxic, hepatotoxic, carcinogenic, and many more. In short, ochratoxins are generally more toxic than aflatoxins, as ochratoxins can cause more severe diseases toward humans and animals.
            Other than that, aflatoxins are mainly found in plants such as Aspergillius flavus and A. parasiticus. Meanwhile, ochratoxins generally can be found in in food, for example, cereals, beans, dried fruits, and also in beverages such as beer, wine and coffee. To continue, ochratoxins have higher reactivity than aflatoxins as ochratoxins contains more functional groups than aflatoxins. Last but not least, not all aflatoxins have contained toxicological properties as there are non-toxic aflatoxins, and ochratoxins are completely considered as highly toxic compounds.
            For the similarities between aflatoxins and ochratoxins, first of all, both of aflatoxins and ochratoxins have contained toxicological properties, in general. Other than that, both aflatoxins and ochratoxins contained various classifications according to the structures and properties. Other than that, both can harm humans’ and animals’ health. Subsequently, both contained coumarin-derived structures, and both originated via shikimate pathway. Lastly, both aflatoxins and ochratoxins may not give toxicological effects if both have been taken in very small amounts inside the body systems.
            For structural classifications of aflatoxins, first of all, the aflatoxin B1, which is the most toxic and carcinogenic aflatoxin, contain mostly unsaturated structure. In addition, there are no hydroxyl groups that can be found in this aflatoxin B1 structure. Then, the other classification is aflatoxin B2. This aflatoxin B2, accoding to Basappa (2009), has been derived from aflatoxin B1. This has been formed via incubation of aflatoxin B1 with hydrogenation reaction that occurred at aflatoxin B1 structure, hence make aflatoxin B2 to be also known as dihydroaflatoxin B1 which is less toxic than the aflatoxin B1 origin.
            Then, for aflatoxin G1, this type of aflatoxin shares a lot of similarities with aflatoxin B1; only slight difference is that this aflatoxin G1 might contain hydroxyl group in the structure, which cannot be found in the aflatoxin B1 structure. Meanwhile, the aflatoxin G2, likewise aflatoxin B2, is the derivative of aflatoxin G1 which also can be known as dihydroaflatoxin G1. For the toxicological properties, both aflatoxin G1 and aflatoxin G2 are less toxic that their respective aflatoxin B1 and aflatoxin B2.
            Subsequently, from those four main classifications of aflatoxins, there are lot aflatoxin metabolites and derivatives can be formed from those structures. These have included aflatoxins M1, M2, GM1 and GM2, aflatoxin B2a and G2a, aflatoxin M2a and GM2a, aflatoxin Q1, aflatoxin P1, aflatoxin B3 which also known as parasiticol, aflatoxin R0 (Aflatoxicol), aflatoxicol H1, aflatoxicol M1, reduced aflatoxin B1 and B2, aflatoxin B1-2-3-oxide, and lastly, O-alkyl aflatoxin.
Among the most notable aflatoxin derivatives is aflatoxin B2a which is generally not active, or non-toxic. Other than that, aflatoxin P1 has been noted to become non-toxic when exposed to chicken embryo. Moreover, aflatoxin P1 (parasiticol) is among the least toxic among the toxic aflatoxin derivatives, found in poultry productions. In addition, aflatoxin R0 (aflatoxicol) can be highly discovered in bird, rabbit, fish, rodents and livestock, containing plunge mutagenic properties. Lastly, the O-alkyl aflatoxin “has been identified as major adduct formed between aflatoxin B1 and DNA or RNA” (Basappa, 2009).
            There are some classifications regarding ochratoxins, which regarding to the source of the ochratoxin compounds. However, as highly opposed to aflatoxins which has a lot of discovered categories and derivatives, there are only one most significant ochratoxin group which has been discovered until now, which is known as Ochratoxin A (OTA). This OTA is originated from
Aspergillus species. 
            According to Reddy and Bhoola (2010), this OTA can stay within a very long time in human bodies, mostly found in serum sample. As a result, this OTA can stay in a very long time in the human bodies; hence can cause severe effects towards human health. In fact, OTA is among the most toxic yet dangerous mycotoxin. This is because; this OTA contains a lot of human health toxins, such as neurotoxins, hepatotoxins, nephrotoxic. This has resulted on various important body system defects, which includes neurotransmitter, digestion systems, secretory systems and many more. In short, this OTA can cause severe diseases towards human bodies as well as animals.
Unfortunately, until now, the other classifications of ochratoxins are still cannot be discovered. There is research about ochratoxins in pennicilium species, however, the research about the types of ochratoxin contained is still yet ongoing.
            The synthesis of Aflatoxin B1 begins with Wittig-carboxymetyl addition reaction on coumarin enoate ester structure, forming enal. Then, the enal undergoes allylic oxidation, resulting formation of new enal enoate ester. After that, conjugated reduction occurred, and difuranocoumarin begin to form.
After the difuranocoumarin formation, acetylation of OBn occurred, to be replaced with OAc functional group. After that, Penchmann reduction occurred, followed by formation of methyl dihydroisodifuranocoumarin (with formation of new six-membered ring ester). After the formation, hydration occurs, forming carboxylic acid group. Then, Friedel-craft acylation occurs, forming new five-membered ring ketone. Before the formation of the aflatoxin, reduction has occurred, lactone turns to lactol, followed by ester pyrolysis, resulting the formation of desired aflatoxin B1 product.

As compared to the synthesis of the aflatoxins, ochratoxins are not the secondary metabolite, instead just contaminants of phenylalanine reacted with coumarin derivatives, thus the synthesis of this particular ochratoxin compound is much simpler compared to aflatoxins synthesis.
 The synthesis begins with formation of malonyl-CoA from the polyketide synthase of acetyl-CoA and malonate. Then the malonyl-CoA forms cyclic compound with esterifications and several condensations, to form mellein. Subsequently, the mellein undergo carboxylation to form ochratoxin β, and then the ochratoxin β turned into ochratoxin α via para-chlorination reaction.

 At the same time, the shikimate pathway reactions has occurred which converted shikimic acid to phenylalanine. And finally, the formed phenylalanine contaminated with ochratoxin α, and the ochratoxin A finally has been produced. The final reaction involves ochratoxin A.

Assalamualaikum (welcoming remarks)


Alhamdulillah setelah dekat 6 tahun lebih gak la bersara daripada tulis blog kini saya kembali lagi dalam bidang penulisan blog. Terlalu banyak mehnah dan tribulasi kehidupan terpaksa dihadapi dalam kehidupan sepanjang 23 tahun lebih hidup setakat ni dan Alhamdulillah sehingga hari ini Allah masih lagi mengizinkan saya hidup, serta memberi peluang buat diri ini untuk memperbaiki diri inshaAllah amiin allahumma amiin.

Sebagai muqoddimah bagi "comeback" bagi blog ini ( ini setelah "deactivate" dalam tahun 2011 atas alasan "xde idea nk tulis apa kat blog" buat pertamanya marilah kita sama2 merafa'kan setinggi-tinggi kesyukuran kepada Allah kerana memberi peluang kepada kita untuk sama2 hidup di muka bumi Allah ini, serta menerima banyak nikmat di mana sesungguhnya kalau nak kira banyak mana nikmat yang Allah kurniakan buat kita maka sesungguhnya tidak akan terhitung jumlah nikmat itu (sebagaimana dinukilkan di surah Ibrahim ayat 34 dan surah An-Nahl ayat 18). Antara nikmat terbesar yang telah dikurnuiakan buat kita ialah nikmat Iman dan Islam. Alhamdulillah thummalhamdulillah. Serta selawan dan salam buat Rasulullah S.A.W. kerana berkat perjuangan baginda dan para sahabat dapat kita kecapi nikmat iman dan Islam sehingga hari ini. (mcm ayat muqoddimah tazkirah pulak hehe).

Sebenarnya dah lama dah plan nak aktif balik dalam penulisan blog ni (macam zaman muda2 dulu (cakap jela zaman sekolah dulu haha)). Dari tahun lepas lagi. Tapi atas alasan busy (cakap jela malas) dekat setahun hasrat nak comeback (la sangat) tu terbantut huhu. Dan Alhamdulillah hari ini dapat sedikit suntikan semangat untuk kembali dalam penulisan blog inshaAllah. Harap usaha ini tidak la terhenti setakat ini. Doakan kekuatan untuk saya berkongsi sedikit daripada ilmu Allah yang maha luas itu (surah al-Kahfi ayat 109, surah Luqman ayat 27) inshaAllah moga bermanfaat buat kalian.

InshaAllah untuk permulaan, blog saya ini akan terbhagi kepada beberapa segmen seperti:

  • Alkisah (pasal pengalaman hidup, kenangan pahit manis semua la (sedikit flashback sebagai panduan kita semua inshaAllah)
  • Tazkirah (general tazkirah)
  • Sifat mahmudah
  • Info2 (juga merangkumi isu semasa)
  • Info jalan raya (antara minat saya ialah mengenai jalan raya)
  • English corner (to improve my English performance inshaAllah)
  • Lain2 (selain drp segmen2 di atas)

Akhir kalam, selamat datang ke blog saya. Moga bermanfaat buat kalian inshaAllah....