Fatty acid composition of sterol esters from Citrus sinensis,C. paradisi,C. limon aurantifolia and C. limettioides sacs

The fatty acid compositions of sterol esters from 4 citrus species, viz, orange. grapefruit, lemon and lime, were determined by GLC. Each species possessed its own intrinsic fatty acid pattern which could be used to differentiate it from the other species. In most cases varieties within a species had fatty acid patterns which could be used for varietal differentiation. In all citrus tested except Columbia lime, the major acid was linoleic acid; this acid varied from 10 to 56% of the total acid content. The ratios of 16/16:1 were distinct for each citrus species. The C₂₂-C₂₉ fatty acids were prevalent in citrus sterol esters ranging from 6·5% for some orange and grapefruit varieties to over 41% for two lime varieties. In all varieties C₂₄ was the most prominent of these longer chain fatty acids. Argentation TLC indicated that these longer chain fatty acids primarily were esterified to dimethyl sterols. ft*|One of the laboratories of the Southern Region, Agricultural Research Service, U.S. Department of Agriculture.     

Fatty acids of triglycerides from Citrus juice sacs

The fatty acid composition of trigylcerides from oranges, grapefruit, lemons and limes, was determined by GLC. Each species possessed its own intrinsic fatty acid pattern which might be used to differentiate it from the other species. The five major acids in all species were palmitic, palmitoleic, oleic, linoleic and linolenic. Collectively these acids comprised greater than 92% of the total acid content. Lemons were distinguished from all other species by their higher 16/16:1 ratios while grapefruit showed the highest total percentage of 16 and 16:1 acids. Lemons and limes contained higher percentages of branched-chain acids than oranges and grapefruit.     

Fatty acids of triglycerides and sterol esters from duncan grapefruit,dancy mandarin and their tangelo hybrids

The fatty acid composition of the triglycerides and sterol esters of juice sac lipids were determined in Duncan grapefruit, Dancy mandarin and three of their tangelo hybrids. The fatty acid profiles of Orlando and Minneola tangelos resembled those of the Dancy mandarin parent more than those of the grapefruit. The profiles of Seminole tangelo were different from those of both parents and of its sister hybrids.     

Saturated and mono-unsaturated long-chain hydrocarbon profiles from mandarin juice sacs

The long-chain saturated and mono-unsaturated hydrocarbon content of the juice sacs of five mandarin cultivars (Mediterranean, Honey, Wilking, Kinnow, King) were examined. Normal homologues accounted for more than 47% of the saturated and more than 75% of the monoene hydrocarbons. In the saturated fraction the major hydrocarbon was n-C₂₅ but in the monoene fraction n-C₂₅ predominated in Kinnow and King while C₂₉ predominated in Mediterranean, Honey and Wilking. All five cultivars could be differentiated from each other and from other citrus species by their hydrocarbon patterns. The noticeably high normal/iso ratios of saturated C₂₃ and C₂₅ hydrocarbons previously shown to be characteristic of mandarin species, Citrus unshiu and C. reticulata, were also found in C. nobilis and C. deliciosa.     

Variation of the long-chain hydrocarbon pattern in different tissues of duncan grapefruit

Long-chain hydrocarbons were analyzed in peel wax, leaf wax, stem, seeds and juice sacs of Duncan grapefruit. The distribution of alkanes in juice sacs     

Saturated mono-unsaturated long-chain hydrocarbon profiles of sweet oranges

Three varieties of midseason oranges, viz. Jaffa, Homosassa and Queen, were examined for their saturated and mono-unsaturated hydrocarbon composition in juice sacs. Hydrocarbons were isolated by lipid extraction of the juice sac powders followed by column, thin-layer and AgNO₃-TLC. After hydrogenation, the mono-unsaturated fraction and the saturated fraction were analyzed by GC. In the saturated fraction, the dominant linear hydrocarbon was C₂₃ while C₂₅ predominated in the monoene fraction. iso- And anteiso-branched hydrocarbons comprised between 53 and 63 % of the saturated fraction and only 20–26 % of the monoene fraction. Queen differed from Homosassa and Jaffa in the accumulation of higher percentages of saturated iso- and anteiso-branched hydrocarbons and conversely, showed lower percentages for these branched structures in the monoene fraction. Based on the total relative percentages of the three isomeric hydrocarbons, Homosassa could not be differentiated from Jaffa. The overall profiles for these two oranges, however. showed noticeable differences.     

The fatty acid composition of Ulothrix aequalis lipids

Fatty acid composition of the total lipids isolated from the fresh-water green alga Ulothrix aequalis shows that they resemble marine green algal lipids in having a high proportion of 16:4 ω-3 but differ in having only trace amounts of 18:4 ω-3. The distribution of ω-3 acids in the MGDG and DGDG fractions resembles that in green seaweeds and higher plants with the 16:4 ω-3 distribution in the Ulothrix fractions resemblmg that of 18:4 ω-3 in the corresponding fractions of the seaweeds.     

Characterization of citrus pectin samples extracted under different conditions: influence of acid type and pH of extraction

Background and Aims

Pectin is a complex macromolecule, the fine structure of which is influenced by many factors. It is used as a gelling, thickening and emulsifying agent in a wide range of applications, from food to pharmaceutical products. Current industrial pectin extraction processes are based on fruit peel, a waste product from the juicing industry, in which thousands of tons of citrus are processed worldwide every year. This study examines how pectin components vary in relation to the plant source (orange, lemon, lime, grapefruit) and considers the influence of extraction conditions on the chemical and macromolecular characteristics of pectin samples.

Methods

Citrus peel (orange, lemon, lime and grapefruit) from a commercial supplier was used as raw material. Pectin samples were obtained on a bulk plant scale (kilograms; harsh nitric acid, mild nitric acid and harsh oxalic acid extraction) and on a laboratory scale (grams; mild oxalic acid extraction). Pectin composition (acidic and neutral sugars) and physicochemical properties (molar mass and intrinsic viscosity) were determined.

Key Results

Oxalic acid extraction allowed the recovery of pectin samples of high molecular weight. Mild oxalic acid-extracted pectins were rich in long homogalacturonan stretches and contained rhamnogalacturonan I stretches with conserved side chains. Nitric acid-extracted pectins exhibited lower molecular weights and contained rhamnogalacturonan I stretches encompassing few and/or short side chains. Grapefruit pectin was found to have short side chains compared with orange, lime and lemon. Orange and grapefruit pectin samples were both particularly rich in rhamnogalacturonan I backbones.

Conclusions

Structural, and hence macromolecular, variations within the different citrus pectin samples were mainly related to their rhamnogalacturonan I contents and integrity, and, to a lesser extent, to the length of their homogalacturonan domains.     

Multiple forms of pectinesterase in limes and oranges

Two forms of pectinesterase, apparently similar in MW but differing in charge and response to cation concentration, have been demonstrated in West Indian limes and Washington Navel oranges, and these enzymes have been purified at least 100-fold. In the orange one pectinesterase is located almost exclusively in the peel while the other is located within the segment covers and juice sacs. The location of the two pectinesterases in lime has not been determined.     

Isoenzyme pattern of superoxide dismutase in different varieties of citrus plants

Superoxide dismutases (SOD; EC 1.15.1.1) in leaves from different cultivars of citrus plants were characterized using isoelectric focusing in polyacrylamide gels. The plants studied included Citrus limonum R. (cvs Verna, Fino, and Eureka), C. paradisi Mac (cvs Red Blush and Marsh), C. aurantium L. (cv. Comun), C. sinensis L. Osbeck (cvs Navel, Valencia, and Salustiano), and C. reticulata B. (cv. Satsuma). The three molecular forms of SOD were distinguished from each other by their different sensitivity to cyanide and H₂O₂. In C. limonum leaves, four Cu,Zn-SODs, three Fe-SODs and two Mn-SODs were present. However, in leaves from different varieties of C. sinensis, C. paradisi, C. aurantium and C. reticulata the activity and number of Fe-SOD isoenzymes were lower than in lemon leaves, whereas the number of MN-SOD isozymes was increased. Cu,Zn-SODs did not show significant variations in the different species and cultivars. The identification of Fe-SODs in several species of the plant family Rutaceae extends the small number of higher plants where the presence of these Fe-containing metalloenzymes has been demonstrated. Results obtained may be useful from an evolutionary viewpoint and also in mineral nutrition studies using SOD isozymes as markers of functional metals.     

Plant pathotoxins from Alternaria citri: The minor ACRL toxins

Five host-specific pathotoxins, ACRL toxins II, III, III′, IV and IV′, were isolated from the culture broth of Alternaria citri, the fungus causing brown spot disease of rough lemon. These toxins are related structurally to the major ACRL toxin, toxin I, and to its derivative compound A. Chemical and spectral studies indicated that the ACRL minor toxins were a group of analogous compounds of different chain lengths all of which have a α-pyrone group, in contrast to the dihydro-α-pyrone group in toxin I. Toxin II showed a very low biological activity (ED₅₀ greater than 10 μg/ml) whereas the other minor toxins had slightly higher activities ranging from 1 to 10 μg/ml. The dihydropyrone group in ACRL toxin I was correlated with high biological activity (ED₅₀ = 18–30 ng/ml).     

Fatty acid profiles of esterified sterol glucosides from juice vesicles of citrus fruits

Vesicular lipids of 24 citrus cultivars were extracted and purified, and the esterified sterol glucosides (ESG) separated from other vesicular lipids by chromatography. Fatty acids of the ESG were analysed by gas-liquid chromatography as their methyl esters. Statistical analysis showed that five out of six citrus species or biotypes could be differentiated from each other on the basis of profiles of the five major ESG fatty acids. Differences between midand late-season sweet orange cultivers were detected. Small differences were observed between white- and red-fleshed grapefruit cultivars. Profiles of the minor acids showed higher relative percentages of iso-branched fatty acids in lemons and limes, and higher relative percentages of 12: 0 and 14: 0 fatty acids in mandarin and mandarin hybrids than in other cultivars.     

Structural elucidation of some orange juice carotenoids

The structure of some carotenoids of Valencia orange juice were elucidated by chemical tests and MS of the free pigments and their derivatives. A new apocarotenal was shown to be 3-hydroxy-5,8-epoxy-5,8-dihydro-8′-apo-β-caroten-8′-al. Two UV-fluorescent apocarotenols found recently in avocado were also present. For the pigments previously designated trollixanthin and trollichrome, the new structures 5,6-dihydro-β,β-carotene-3-3′,5,6-tetrol and 5,8-epoxy-5,8,5′,6′-tetrahydro-β,β-carotene-3,3′,5′,6′-tetrol are assigned, both containing a trihydroxylated ring as in heteroxanthin.     

Bakkenolide-A. Its distribution in Petasites species and cytotoxic properties

A rapid GLC method is described for the determination of bakkenolide-A in small amounts of plant material. The distribution of bakkenolide-A among the different lipid classes of Petasites albus is discussed and also the distribution among different parts of the plant during a growing season. Smaller amounts of bakkenolide-A are found in P. hybridus buds and only trace amounts in P. fragrans.Cytotoxicity tests showed bakkenolide-A has marked cytotoxic activity and potential anti-tumour properties.     

Effects of cold hardening on acyl lipids of citrus tissue

Cold hardened and unhardened 8- or 16-month-old citrus plants were examined for differences in fatty acid (FA) content. Unhardened leaves from 8-month-old Valencia scion budded on sour orange rootstock had 29% less FAs than leaves from seedling sour orange. After cold hardening triacylglycerol (TAG) FAs increased 4-fold in Valencia on sour orange and 6-fold in sour orange seedling. The percentage of FAs associated with TAGs for unhardened-hardened 16-month-old Valencia on sour orange tissues were: upper leaves 7–20, lower leaves 6–17, bark 6–9, and roots 57–73%. Cold hardening increased the amount of TAG FAs of 16-month-old Valencia on sour orange in upper leaves by 226% and in lower leaves by 173%. Concentrations of linoleic acid increased by 479% in upper leaves and by 303% in lower leaves. Quantities of lionolenic acid in monogalactosyl diacylglycerols declined by 27% in upper leaves and by 20% in lower leaves.     

Chlorophyll formation and glycine metabolism in laevulinic acid treated barley leaves

Laevulinic acid (LA) inhibited chlorophyll formation and δ-aminolaevulinic acid (ALA) accumulation in dark-grown barley leaves. Mole ratios (ALA: chlorophyll × 8) indicate that LA decreased ALA production by about 30%. The turnover of glycine-[¹⁴C] in 7-day-old leaves treated with LA was 70% slower than in control tissue and this resulted in an increase in endogenous glycine. Total amino acid also increased in LA treated leaves. The data indicate that any contribution made by glycine to ALA synthesis in LA-treated barley leaves would be significantly restricted.