Yang, Liyi (2009-12). Chemopreventive Potential of Sorghum with Different Phenolic Profiles. Master's Thesis. Thesis uri icon

abstract

  • Epidemiological evidence has correlated consumption of sorghum with reduced incidences of gastrointestinal (GI) tract cancer, especially esophageal cancer. There is little evidence on how phenols of sorghum may affect chemoprevention. Seventeen sorghum varieties were screened for phenolic profiles and antioxidant capacity. The ability of crude sorghum extracts to induce NAD(P)H:quinone oxidoreductase (QR, a phase II protective enzyme), and inhibit proliferation of colon (HT-29) and esophageal (OE33) carcinoma cells using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide) and PicoGreen assays, were determined in vitro. 3- Deoxyanthocyanidins, apigeninidin, luteolinidin and their methoxylated derivatives were also investigated for antioxidant capacity, QR inducing and antiproliferative potential. Tannin sorghum generally showed higher antioxidant capacity than non-tannin sorghum varieties. Sorghum varieties containing extractable condensed tannins did not show any significant QR inducing potential; on the other hand, non-tannin sorghums increased QR activity by 1.5-2.7 times; black sorghum (Tx430) was most potent (doubled QR activity at 25 mg/mL, 2.7-fold increase at 100 mg/mL). All sorghum extracts showed relatively strong antiproliferation activity with IC50s (the concentration needed to inhibit cancer cell growth by 50%) of 49.7-883 mg/mL. Tannin-containing sorghums had stronger cancer cell proliferation inhibitory potential (IC50s 49.7-131 mg/mL) than non-tannin sorghums (IC50s 141-883 mg/mL). Total phenol content and antioxidant capacity of crude sorghum extracts positively correlated with their antiproliferative potential (r2 0.71-0.97). Among tested 3-deoxyanthocyanidins, methoxylation on A-ring improved QR inducing potency. 5,7-Dimethoxyluteolinidin had the greatest QR inducing potency (4.3- fold at 100 mM). Methoxylation also improved their antiproliferation potential; the IC50s trend was di-methoxylated (8.3-105 mM) > mono-methoxylated (40.1-192 mM) > apigeninidin and luteolinidin (81.5-284 mM). This study provides information for how phenolic compositions of sorghum and 3-deoxyanthocyanidin structure affect their capacity to induce QR activity and inhibit GI tract cancer cell proliferation. The information is useful to promote the utilization of sorghum in functional foods, beverages, dietary supplements, and other health-related industries. Further study will focus on, fractioned and isolated sorghum phenols, the effect of food processing on their chemopreventive potential, as well as cellular mechanisms involved.
  • Epidemiological evidence has correlated consumption of sorghum with reduced
    incidences of gastrointestinal (GI) tract cancer, especially esophageal cancer. There is
    little evidence on how phenols of sorghum may affect chemoprevention. Seventeen
    sorghum varieties were screened for phenolic profiles and antioxidant capacity. The
    ability of crude sorghum extracts to induce NAD(P)H:quinone oxidoreductase (QR, a
    phase II protective enzyme), and inhibit proliferation of colon (HT-29) and esophageal
    (OE33) carcinoma cells using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-
    diphenyltetrazolium bromide) and PicoGreen assays, were determined in vitro. 3-
    Deoxyanthocyanidins, apigeninidin, luteolinidin and their methoxylated derivatives were
    also investigated for antioxidant capacity, QR inducing and antiproliferative potential.
    Tannin sorghum generally showed higher antioxidant capacity than non-tannin
    sorghum varieties. Sorghum varieties containing extractable condensed tannins did not
    show any significant QR inducing potential; on the other hand, non-tannin sorghums
    increased QR activity by 1.5-2.7 times; black sorghum (Tx430) was most potent
    (doubled QR activity at 25 mg/mL, 2.7-fold increase at 100 mg/mL). All sorghum extracts showed relatively strong antiproliferation activity with IC50s (the concentration
    needed to inhibit cancer cell growth by 50%) of 49.7-883 mg/mL. Tannin-containing
    sorghums had stronger cancer cell proliferation inhibitory potential (IC50s 49.7-131
    mg/mL) than non-tannin sorghums (IC50s 141-883 mg/mL). Total phenol content and
    antioxidant capacity of crude sorghum extracts positively correlated with their
    antiproliferative potential (r2 0.71-0.97).
    Among tested 3-deoxyanthocyanidins, methoxylation on A-ring improved QR
    inducing potency. 5,7-Dimethoxyluteolinidin had the greatest QR inducing potency (4.3-
    fold at 100 mM). Methoxylation also improved their antiproliferation potential; the IC50s
    trend was di-methoxylated (8.3-105 mM) > mono-methoxylated (40.1-192 mM) >
    apigeninidin and luteolinidin (81.5-284 mM).
    This study provides information for how phenolic compositions of sorghum and
    3-deoxyanthocyanidin structure affect their capacity to induce QR activity and inhibit GI
    tract cancer cell proliferation. The information is useful to promote the utilization of
    sorghum in functional foods, beverages, dietary supplements, and other health-related
    industries. Further study will focus on, fractioned and isolated sorghum phenols, the
    effect of food processing on their chemopreventive potential, as well as cellular
    mechanisms involved.

publication date

  • December 2009