Abstract
Physico-chemical
studies of the extracts from Napoleona Vogelli as an alternative source of new
acid-base indicators derived from locally available plants were
investigated. Three solvents phases
(organic, organic/aqueous (50:50) and aqueous) were employed in the extraction
process.
The organic phase extract was readily purified and was used for
further investigation. Thin layer chromatography (TLC) separation of this
extract yielded six components, acid-base, titration of the organic phase
extract produced results quit comparable with phenolphthalein and methyl orange
using 0.01m and 0.10m Na0H and HCL respectively. All the extract and components
were also titrated under similar conditions and proved suitable as indicators
for acid base titrimetry, involving strong acid versus strong base, strong acid
versus weak base, as well as weak acid versus weak base. They were not suitable
for weak acid versus strong base. The calculated PK a value of 9.8 of the
organic extract compound with 9.60 of phenolphthalein confirms the extract as a weak
acid. These values suggest that Napoleona vogelli extracts are a suitable
alternative source of acid-base indicators from local plants.
CHAPTER ONE
INTRODUCTION
In Ebonyi state, many interesting plants abounds with
rich cultural value and hence demands scientific investigation. The studies of
their physiochemical properties are important because people living around the
areas uses the plants as direct foods and supplements, herbal medicines,
ornamentals, and agro-chemicals. The physicochemical studies of substances
involve identification and/or characterization based on their physical and
chemical properties (Solan and Sirry, 2002). Physical properties do not lead to
changes in chemical identity (Soltan and Sirry, 2002) and (Gruden, 2000)
whereas chemical properties can result to alternation in chemical identities
such as pH, toxicity, flammability, colour changes, reactivity with water, etc
(Musoke, 2002), (Geotge et al. 1987) and, (Ekandem and Owor, 1997). An acid-base
indicator may be used to indicate the endpoint of a particular neutralization
reaction, or the ph of a system (Gruden, 2000), and (Geroge et al., 1987).
Many substances, both naturally
occurring and synthetic, display colours that depend on the pH of the solutions
in which, they are dissolved. Some of the substances which have used for
centuries to indicate the acidity or alkalinity of water, are still employed as
acid/base indicators. Many plants or plant parts contain chemicals from the
naturally coloured anthocyanin family of compounds. They are red in acidic and
blue in basic solutions (Geroge et al. 1987). The dyes/pigments in plants are
natural substances commonly used as acid-base indicators and are weak acids and
bases (Geroge et al. 1987), (Ekandem and Owor, 1997) and (Okoye and Oforka,
2009). Indicators used in the laboratories are coloured organic dyes that gives
different colours in acidic and basic media. Many indicators can be extracted
from plants and some graden plants can be used as ph indicators, e.g. Napoleona
Vogelii Hook (8 - 12) (Francis, et al. 1996), (Finar, 2004), (Fuleki, 1979),
(Ageti et al., 2005)and (Del et al.,
2004).
Napoleona Vogelii Hook (popularly
known as “Udarutobo or Nkpodo”, among the Igbo speaking people) is one of the
most potent species of lecythidaceae that is richly endowed with pigments. The
fruits are green unripe, and reddish-orange ripe. (Francis, et al., 1966)
defined it as “a genus of about 125 species of trees native to the tropical
rainforest of Africa, and are classified in the family of lecythidaceae, and
subfamily of Vogelii Hook. An ever-prickly leafy tree, growing about 2.50m to
5.0m tall, Napoleona Vogelii Hook is a sweet and edible fruitfound in holly – a
tree with hard prickly leaves all through the year and the ripe fruits in the
dry seasons. The trees are grown widly on a prickly rocky bush in most parts of
Ebonyi state of Nigeria, particularly along
the Akpoha – Amasiri axes. The fruits are widely eaten by bush monkeys hence
the local name “udautobo”, meaning monkey apple. Farmers and rural dwellers
also eat the flesh of Napoleona Vogelii Hook fruits. The colourful skins also
attract the attention of other animals, which may eat the fruits and disperse
the seeds. Many researchers such as (Munoz-Espada et al., 2004), (Hosseinian
and Beta, 2007), (Wada and Ou, 2002) and (Siriwoharn et al., 2004) have noted
that the red coloration of the fruits may camouflage them from herbivores blind
to red wavelengths, or signal un-palatability, since anthocyanin often
coincides with unpalatable and phenolic compounds. Nature, primitive
agriculture and plant breeding have produced various crops containing
anthocyanins (Finar, 2004), (Fuleki, 1979), (Agati et al., 2005), (Del et al.,
2004), (Munoz-Espada et al. 2004), (Hosseinian and Beta, 2007) and (Wada and
Ou, 2002), including Napoleona Vogelii
Hook fruits, blue- or red-fleshed potatoes, and purple or red broccoli cabbage,
bred conventionally for high anthocyanin content by crossing wild relatives
with the common tomato to large and more palatable fruit (Agati et al., 2005)
and (Del et al., 2004)
Aims and Objectives of the Research
The purpose of this research was to investigate the
Napoleona Vogelii Hook fruit pigments as a potential source of acid-base indicator.
Scope of the Research
The scope of this work is the limit to which I got to,
in the actualization of my aim. Ranging from, extraction of the indicator from
the three major phases thin layer chromatographic separation, titration of the
extracts from each case and compassion with some standard indicators to as
certain the level of accuracy and precision of the standard indicator.