Extraction of M.oleifera and J. curcas materials can be done both by
conventional and non-conventional methods. Non-conventional methods
include ultrasound, pulsed electric field, enzyme digestion, extrusion,
microwave heating, ohmic heating, supercritical fluids extraction and
phytonic extraction with hydrofluorocarbon solvents. Herrera and Luque
de Castro (2004) and Li et al., (2005) used Ultra sound extraction
process to extract phenolic compounds from strawberries and chlorogenic
acid from fresh leaves, fresh bark and dried bark of Eucommia ulmodies
Oliv. Guderjan et al. (2005) and Corralesa et al. (2008) recovered
phytosterols from maize, isoflavonoids (genistein and daidzein),
soybeans anthocyanins and grape by-product using pulse electric field.
Landbo and Meyer (2001), Li et al., (2006) showed improved release of
phenolic compounds from Ribes nigrum pomace and five citrus peels
(lemon, Meyer lemon, grapefruit, mandarin and orange) using enzymatic
digestion. Pan et al. (2003) and Chiremba et al. (2012) extracted
phenolics from coffee, tea waste, bran, flour fractions of sorghum and
maize of different hardness by microwave assisted extraction. Mroczek
and Mazurek (2009) and Erdogan et al., (2011) extracted lycorine and
galanthamine from Narcissus jonquilla and gallocatechin (GCT), catechin,
epicatechin gallate, caffeic acid, chlorogenic acid and myricetin and
total phenolic contents were recovered from various parts of Anatolia
propolis pressurized liquid extraction. Saldana et al., (1999) and
Khorassani and Taylor (2004) extracted purine alkaloids (caffeine,
theobromine, and theophylline) from Ilex paraguaryensis, naringin
(flavonoid) from citrus fruits and polyphenols and procyanidins from
grape seeds using super critical fluid extraction. Whereas conventional
methods include extraction with maceration, infusion, decoction,
digestion (Ncube, 2008), percolation (Handa et al., 2008),
aqueous-alcoholic extraction by fermentation and hot continuous
extraction (soxhletor) (Nikhal et al., 2010). For aromatic plants,
hydrodistillation techniques (water distillation, steam distillation,
water and steam distillation), hydrolytic maceration followed by
distillation, protoplast extraction, microdistillation,
thermomicrodistillation and molecular distillation are used (Vankar,
2004). However, extraction with soxhelator is mostly used. The advantage
of this system is that instead repeated use of large amount of solvent
being passed through the sample, just one batch of solvent is recycled.
Non conventional technique has advantage over the conventional one. It
makes use of less hazardous chemical, safe solvents auxiliaries, energy
efficiency machineries, use of renewable feedstock, pollution free
equipments, and safer chemistry for the prevention of accident.
Therefore the ever growing demand to extract plant bioactive compounds
encourages continuous search for convenient extraction methods. The
advancement chromatographic techniques and awareness about environment
are two important factors for the development of most nonconventional
extraction processes. Incorporation and development of hybrid methods
should also be used for better recovery of bioactive molecules from
plants. Proper choice of standard methods influences extraction
efficiency.
Successful determination of biologically active compounds
from plant material is largely dependent on the type of solvent used in
the extraction procedure. The choice will also depend on the targeted
compounds to be extracted (Das et al., 2010). The polarity of the
targeted compound is the most important factor for solvent choice. Along
with that molecular affinity between solvent and solute, mass transfer,
use of co-solvent, low toxicity, ease of evaporation at low heat, rapid
physiologic absorption of the extract, preservative action, inability
to cause the extract to complex or dissociate. The other factors
affecting the choice of solvent are – quantity of phytochemicals to be
extracted, rate of extraction, diversity of compounds to be extracted, ,
ease of subsequent handling of the extracts and financial feasibility
(Eloff et al., 1998).
