Limonoid

Chemical structure of the prototypical limonoid limonin

Limonoids are phytochemicals of the triterpenoid class which are abundant in sweet or sour-scented citrus fruit and other plants of the families Cucurbitaceae, Rutaceae, and Meliaceae.[1] Certain limonoids are antifeedants such as azadirachtin from the neem tree.[2]

Chemically, the limonoids consist of variations of the furanolactone core structure. The prototypical structure consists of four six-membered rings and a furan ring. Limonoids are classed as tetranortriterpenes.

Structural formula of Limonin Structural formula of Nomilin Structural formula of Nomilinsäure
Limonin Nomilin Nomilinsäure

Occurrence

Limonoids occur in the seeds of citrus plants, for example in grapefruit, lemon, orange, and mandarin, as well as in other species. They are present both as glucosides and in free form (i.e., as the aglycone). The quantitatively predominant glucoside is nomilinglucoside, whereas the most abundant free aglycone is limonin. Other compounds occurring both in free form and as glucosides include nomilic acid, obacunone, and deacetylnomiline. The glucosides account for approximately 0.31% to 0.87% of the dry weight of the seeds.[3] Limonoids are also present in the leaves of the respective plants, which are therefore used in folk medicine as herbal infusions.[4] Azadirachtin is a limonoid found in the seeds of the Niembaum and exhibits a strong insecticidal effect.[5]

Citrus

Citrus fruits contain the limonoids limonin, nomilin and nomilinic acid, while both neem seeds and leaves contain the limonoid azadirachtin, although higher concentrations are present in the former.

Chisocheton erythrocarpus

Eight previously unknown limonoids were identified via spectroscopy in the fruits of Chisocheton erythrocarpus gathered in Malaysia. These compounds were dubbed erythrocarpines after the species epithet. The same study tested several preparations of C. erythrocarpus extract as larvicidal agent against Aedes aegypti mosquitoes; they found that 1000 ppm of DCM extract resulted in 100% mortality of larva 24 hours after exposure.[6]

Pharmacological effect

Numerous potential applications of limonoids have been investigated. Early research attributed strong antioxidant activity to these compounds.[7] However, subsequent studies refuted this assumption. In fact, the total antioxidant capacity (TAC) of limonoids is significantly lower than that of established antioxidants such as ascorbic acid or butylhydroxytoluene (BHT).[8] Of greater importance is the physiological activity of limonoids. They have demonstrated antipyretic[4], antibacterial, and antiviral effects.[9] They have also been successfully applied in the treatment of malaria.[4] Furthermore, their potential as anticarcinogenic agents has been investigated in breast, colon, pancreatic, and liver cancer, as well as in leukemia.[10] In addition, certain limonoids have been shown to reduce cholesterol release and thus exhibit antiatherogenic properties.[8]

Undesirable effects

Limonoids may present challenges in fruit juice production. In particular, the removal of the bitter compound limonin is necessary to improve the sensory quality of the juices.[11]

See also

References

  1. ^ Amit Roy and Shailendra Saraf (2006). "Limonoids: Overview of Significant Bioactive Triterpenes Distributed in Plants Kingdom". Biol. Pharm. Bull. 29 (2): 191–201. doi:10.1248/bpb.29.191. PMID 16462017.
  2. ^ Donald E.Champagne; Opender Koul; Murray B. Isman; Geoffrey G. E.Scudder; G. H. Neil Towers (1992). "Biological activity of limonoids from the rutales". Phytochemistry. 31 (2): 377–394. doi:10.1016/0031-9422(92)90003-9.
  3. ^ Yoshihiko Ozaki, Chi H. Fong, Zareb Herman, Hisao Maeda, Masaki Miyake, Yasushi Ifuku, Shin Hasegawa (January 1991), "Limonoid Glucosides in Citrus Seeds", Agricultural and Biological Chemistry, vol. 55, no. 1, pp. 137–141, doi:10.1080/00021369.1991.10870551{{citation}}: CS1 maint: multiple names: authors list (link)
  4. ^ a b c Cite error: The named reference Römpp was invoked but never defined (see the help page).
  5. ^ A.J. Mordue (Luntz), A. Blackwell (November 1993), "Azadirachtin: an update", Journal of Insect Physiology, vol. 39, no. 11, pp. 903–924, doi:10.1016/0022-1910(93)90001-8
  6. ^ Ngadni, Muhammad Afiq; Chong, Soon-Lim; Hazni, Hazrina; Asib, Norhayu; Ishak, Intan Haslina; Mohmad Misnan, Norazlan; Supratman, Unang; Awang, Khalijah (2024-06-01). "Limonoids from the fruits of Chisocheton erythrocarpus and their mosquito larvicidal activities". Phytochemistry. 222 114092. doi:10.1016/j.phytochem.2024.114092. ISSN 0031-9422.
  7. ^ Cite error: The named reference Koller was invoked but never defined (see the help page).
  8. ^ a b Andrew P. Breksa, Gary D. Manners: Evaluation of the Antioxidant Capacity of Limonin, Nomilin, and Limonin Glucoside, Journal of Agricultural and Food Chemistry, Nr. 54, 2006, S. 3827–3831, doi:10.1021/jf060901c.
  9. ^ Cite error: The named reference Roy was invoked but never defined (see the help page).
  10. ^ Jinhee Kim, Guddadarangavvanahally K. Jayaprakaska, Bhimanagouda S. Patil: Limonoids and their anti-proliferative and anti-aromatase properties in human breast cancer cells, Food & Funktion, Nr. 4, 2013, S. 258–265, doi:10.1039/C2FO30209H.
  11. ^ Stéphane C. Fayoux, Ruben J. Hernandez, Robert V. Holland: The Debittering of Naval Orange Juice Using Polymeric Films. In: Journal of Food Science., Nr. 72, 2007, S. E143–E154, doi:10.1111/j.1750-3841.2007.00283.x.
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